THE NEUROLOGIC EXAMINATION Brad Cole, MD

The neurologic history and physical examination are the most important tools in the neurologic diagnosis. Although confirmatory laboratory data, including modern imaging techniques such as CT scanning and magnetic resonance imaging (MRI) have provided further accuracy in neurologic diagnosis, the history and physical examination remain the mainstays.

These lectures will focus on the interpretation of the neurologic examination, not proficiency in performing the exam. During the neurology clerkship in the third year we will focus on the “how to” of the exam. Interpreting the neurologic examination requires an understanding of the basic neuroanatomical pathways, which will be explained in this handout. In addition, these lectures will form the basis for understanding the unknown case studies.

The neurologic diagnosis can be divided into two types: Anatomic and Etiologic

A. The anatomic diagnosis localizes the lesion within a specific area of the neuroaxis. Clinicians view the neuroaxis as follows: cortical, subcortical, brain stem and cerebellum, spinal cord, anterior horn cell, nerve root, plexus, peripheral nerve, neuromuscular junction, and muscle. Findings on the neurologic examination are critically important in making a correct anatomical diagnosis which should always be the first goal as you approach a patient with a neurological problem. Thus, neurologists are known for asking the question, “Where is the lesion?” After making this diagnosis, the etiologic diagnosis is pursued.

B. The etiologic diagnosis specifies the cause of the lesion, and is mainly obtained from information provided by the neurologic history. The time course of the illness often helps define the etiology of the anatomical lesion. Several examples:

1. Lesions of sudden onset are typically due to disease of the cerebrovasculature, such as a stroke.

2. Slowly progressive focal lesions are more likely due to expanding mass lesions, such as a tumor or abscess.

3. Lesions with exacerbating and remitting courses are sometimes due to demyelination, such as can be seen with .

4. Relentlessly progressive lesions involving all areas of the nervous system are often due to degenerative disorders of the nervous system, such as Alzheimer’s disease.

The Neurologic History

The History of the Present Illness (HPI) consists of an accurate, chronological description of the patients presenting illness. This is critical and requires great attention to the details. For an acute spell (such as seizure), you must obtain a minute by minute account of the event. This means talking to people that witnessed the event. For a chronic complaint, it is important to get the details of how the condition has progressed (month by month). Patients often gloss over important facts or emphasize in great detail what other physicians have told them. For example, a patient may present to you with a complaint of episodic dizziness without volunteering a great deal of additional information. It is your job to painstakingly have the patient take you through each event in excruciating detail. The following account would be a typical interaction with a dizzy patient:

• Patient: I’ve been feeling dizzy recently • Doctor: Tell me what happens • Patient: I just get dizzy one in a while, that’s all. It’s hard to explain. One doctor told me that is was probably a virus. I saw Dr. X who ordered a brain scan, and then he sent me to an ear, nose, and throat doctor who did some other studies and thought that….. • Doctor: Tell me about the first time you noticed the dizziness • Patient: Oh, it’s been going on for quite a while. I figured it was probably the flu at first. • Doctor: Tell me about the first time • Patient: I was at home and I just felt dizzy. I wish that I could describe it better • Doctor: What were you doing at the time • Patient: I was just rolling over in bed • Doctor: Use another word besides “dizzy” to describe what you felt at that moment. • Patient: I felt like I was on a boat and the whole room seemed to be moving around. I also felt nauseated and I threw up. It was awful. That’s about it. Then I went to see my doctor to try and…. • Doctor: First, tell me what happened next at home that day. • Patient: That sea-sick feeling lasted about 10 seconds and I thought I was going to die. Then it was over and I felt okay until it happened later that afternoon. • Doctor: Have you noticed that rolling over in bed often brings on these spells? • Patient: Yeah. And it’s funny that you ask, but it seems to often happen when I roll over or turn my head to the right. That will bring it on almost every time. Not that that means anything.

Notice how the physician had to continually focus the patient to give a simple account of the symptoms. The above history is classic for a condition called benign positional vertigo. If the physician had given up half way through the history and moved on to the physical examination, all

the sophisticated testing in the world would not have arrived at the correct diagnosis. Attention to the details of the history is invaluable and represents the single most important factor in arriving at the correct diagnosis. Although the neurologic examination is an elegant exam that can often accurately localize a lesion, it is still the history that provides the correct diagnosis in most cases.

The Neurologic Examination

The neurologic examination is typically divided into eight components: mental status; language and speech; cranial nerves; motor examination; sensory examination; cerebellar function; reflexes; and gait.

1. Mental Status

The mental status exam is an extremely important part of the neurologic examination that is often overlooked. Assessing cognition implies evaluating higher cortical functions.

The following is an example of common questions that are asked during the mental status examination (you do not need to memorize this for now):

A. Orientation: To person, place, time, and situation B. Memory: Including immediate recall, recent and remote memory. The patient is asked to remember 4 objects (i.e. Boston, Mr. Johnson, red car, and tunnel), and after five minutes of distraction is asked to recall the objects. C. Attention: The patient is given seven numbers and asked to repeat as many as possible. D. Math: 14 + 18, 14 x 6, 65 – 7, 58/2 E. Construction: Draw a clock with the hands pointing to 11:20, copy a cube. F. Abstraction: Have the patient interpret a simple proverb (“a rolling a stone does no gather moss”). Alternatively, the patient can be asked similarities (“how are an apple and a banana alike?”). Even asking odd questions like “do helicopters eat their young?” can sometimes yield interesting information. A patient with Alzheimer’s disease might reply “I suppose they might”, while a ‘normal’ person would say “What was that?” G. Information: Ask the patient current events or general information (“who is the President, how many weeks in a year, what is an island…”).

There are several standardized mental status exams that yield a score which can be used to assess cognitive function. The Montreal Cognitive Assessment (MOCA) is probably the most common one used today.

In patients who are unable to communicate (the patient is intubated or has a language problem, for example) it is helpful to ask the patient to follow commands:

o Close your eyes (1 step) o Close your eyes and point to the ceiling (2 step) o Touch both shoulders two times with two fingers (3 step)

• Damage to large areas of the cerebral hemispheres is required to produce abnormalities of cognition. Two neural structures are required for consciousness: the brain stem reticular activating system, and one cerebral hemisphere. Thus, a patient is unconscious if injury has occurred to both cerebral hemispheres or to the brain stem reticular activating system. A patient is “awake” if the RAS and one hemisphere is intact.

Patients that perform poorly on the mental status examination usually fit in two broad categories, dementia or encephalopathy:

• Dementia is a slowly progressive intellectual decline. Eventually, deterioration in many areas occur: memory, language, calculation, interpersonal communications, motor function, gait, and judgment. • Encephalopathy refers to an acute or subacute change in the patient’s mental state. Delirium is another name for encephalopathy. There are many causes, but often it is due to medications taken inappropriately, an infection, or some other reversible process.

Clinical Differentiation of Encephalopathy and Dementia

Clinical Feature Encephalopathy Dementia Onset Acute/subacute Chronic Course Fluctuating Chronic progressive Attention Prominently impaired Less impaired Reversibility Often Rarely

2. Language and Speech

Two important disorders in this category should always be ruled out: dysarthria and aphasia. Dysarthria is a speech disorder, while aphasia implies a language abnormality. Simply listening to the patient describe his or her complaint is an excellent opportunity to evaluate speech and language function.

• Dysarthria (slurred speech) can be caused by an infinitely long list of neurological and non- neurological abnormalities. An encephalopathic patient, whether due to an infection,

medications, or intoxication, will often have dysarthric speech. Any abnormality of the vocal apparatus (tongue or facial weakness, for example) will also result in dysarthria.

• Aphasia is an acquired disorder in the production or understanding of language due to a lesion involving the dominant cerebral hemisphere. The left hemisphere is dominant in 95% of right-handed people, and 70% of left-handed people. Several tests of language are often required to elicit an abnormality of language function. Having the patient repeat a sentence (“Now that he is gone, we must go away” etc.), will detect an abnormality in most patients with an aphasia. Also, observing the patient name objects, read, and write, are all excellent ways to assess for aphasia. Most common types of aphasia:

Expressive aphasia (motor or Broca’s) is usually seen following a lesion involving the posterior inferior frontal lobe (Broca’s area). An expressive aphasia is marked by significant difficulty producing language, but with relatively preserved understanding. The normal melodious intonation of speech (prosody) is also lost. Naming and repetition are very difficult because of disconnect from Wernicke’s area. Patients with this form of aphasia typically have an associated right , due to involvement of the adjacent motor cortex. Depression is commonly associated with Broca’s aphasia.

Receptive aphasia (sensory or Wernicke’s) is seen with a lesion involving the supramarginal and angular gyri in the parietal lobe, as well as the posterior superior temporal lobe (Wernicke’s area). This aphasia is characterized by fluent speech but with markedly impaired understanding. Typically the patient makes numerous errors in pronunciation and naming called paraphasic errors. These can be of two types. For example, the patient may say “the grass is greel,” or “the grass is blue.” Naming and repetition are also impaired. Patients often lack insight to their lack of language comprehension and ramble on despite a lack of meaningful content.

A large left hemisphere lesion that involves both Wernicke’s and Broca’s area can result in a global aphasia in which the patient cannot understand or speak.

Conduction aphasia results from a lesion of the arcuate fasciculus, which connects Wernicke’s and Broca’s area. Since both of these areas are intact, patients are fluent and can understand, however, when asked to repeat a sentence, patients have difficulty. This type of aphasia is rare clinically yet common on board exams.

Transcortical aphasias are similar to all the above with the exception that repetition is relatively spared. Typically, this is due to watershed ACA-MCA (“mesial frontal”) infarcts1 which spare the primary language areas and the arcuate fasciculus, but damage surrounding language areas in the frontal or temporoparietal regions that are necessary for Broca’s area to function normally. This looks somewhat like Broca’s aphasia but with preserved repetition and is known as transcortical motor aphasia. An MCA-PCA watershed infarct that involves the temporal-parietal cortex around Wernicke’s area can lead to a transcortical sensory aphasia by disconnecting Wernicke’s area from the surrounding cortical areas. This looks somewhat like Wernicke’s aphasia but with preserved repetition. In this condition, the patient can’t understand well in order to repeat sentences, but they might “echo” back words they hear during conversation – a condition known as echolalia. A mixed transcortical aphasia refers to impaired fluency and comprehension (i.e. global aphasia) but with intact repetition and can be due to combined MCA-ACA and MCA-PCA watershed infarcts.

1 Usually due to global hypoperfusion of the brain

3. Cranial Nerves

Olfactory Nerve (I)

This nerve is tested by occluding one nostril and presenting a non-volatile stimulus (coffee, spices, etc.) to the other nostril. This is then repeated on the opposite side. Irritative substances (such as ammonium carbonate – smelling salts) should not be used, since this will stimulate the trigeminal nerve pain fibers rather than olfactory fibers.

Smell should be evaluated after head trauma, because the olfactory nerve may be sheared off as it penetrates the cribriform plate. Meningiomas (benign tumors that originate from the meninges) also cause neurologic loss of smell by invading the cribriform plate. The most common cause for loss of smell, however, is non-neurologic and is due to inflammation of the nasal mucosa during an upper respiratory infection.

Optic Nerve (II)

Three components of the optic nerve are typically evaluated: visual acuity, visual fields, and the ophthalmoscopic examination.

A. Visual Acuity: For neurologic purposes, corrected visual acuity is tested (with eyeglasses or contact lenses). Each eye is checked individually. Visual acuity is checked by means of a Snellen chart or a near card. Visual acuity measures only macular vision, which is the central 5º of the visual field.

• While visual acuity is a reflection of the integrity of the entire visual system, including the refractile components (cornea, lens, vitreous humor, retina, optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, optic radiations, and the occipital cortex), only lesions anterior to the optic chiasm affect visual acuity. This is because visual information from one eye crosses to both hemispheres at the optic chiasm and half of an intact macula does not impair visual acuity. Thus, only a bilateral lesion posterior to the optic chiasm could affect visual acuity.

• A young patient that presents with subacute loss of visual acuity in one eye is often due to demyelination of the optic nerve (optic neuritis). This is typically part of multiple sclerosis, in which various areas of the central nervous system lose myelin. Remember that even though the optic nerve is called a cranial nerve, cranial nerves I and II are

really part of the central nervous system and are myelinated by oligodendrocytes, not Schwann cells.

B. Visual Fields: These are evaluated by the confrontation method. In this method, the examiner stands directly in front of the patient, usually 2-3 feet away. The patient is asked to cover one eye. With the patient fixating on the examiner’s nose, finger counting is then done in all four quadrants (the finger-wiggle technique is sub-optimal). Each eye is checked individually.

Lesions of the visual pathways: 1. Any lesion anterior to the optic chiasm (pre-chiasmal) of the optic nerve or retina results in monocular visual loss. This can vary depending on the etiology and severity of the lesion.

2. Chiasmal lesions affect the crossing nasal retinal visual fibers. Since the nasal retina “sees” the temporal visual field, patients have a bitemporal hemianopia.

3. Optic Tract lesions typically result in a contralateral incongruous homonymous hemianopia since the visual pathways are rotating in this location. “Incongruous” means that the visual deficit is not identical in both eyes.2 Destructive lesions of the lateral geniculate nucleus have a similar appearance and will be discussed in the stroke lecture next year.

2 Most review books show optic tract lesions as a complete contralateral congruous homonymous hemianopia (don’t be confused by this)

4. Destruction of the optic radiations in the temporal lobe (Meyer’s loop) results in a contralateral “pie in the sky” visual field deficit.

5. Destruction of the optic radiations in the parietal lobe involves a larger deficit of the inferior quadrant.

6. A complete destructive lesion of the optic radiations such as occurs with an MCA stroke, will result in a complete contralateral homonymous hemianopia.

7. An occipital lesion that involves the entire occipital lobe will result in a contralateral homonymous hemianopia as seen in #6. In a PCA stroke, however, the macular fibers may be spared since the MCA and PCA both supply the macular fibers.

C. Pupillary Light Reflex – covered under cranial nerve III.

D. Ophthalmoscopic Examination: The retina is evaluated with an ophthalmoscope. The optic disc, surrounding retina, blood vessels and macula can be visualized. In addition, by changing the plane of focus on the ophthalmoscope, one can visualize the cornea and lens.

• Besides looking at the more anterior portions of the eye (for example, looking at the lens for cataracts), one can also look at the retina for evidence of increased intracranial pressure (optic disc swelling or papilledema; occurs with mass lesions in the brain), demyelination of the optic nerve (pallor of the optic disc; occurs in multiple sclerosis), and many other valuable retinal changes. The optic nerve is the only portion of the central nervous system that you can actually “see” on the neurologic examination.

The ophthalmoscopic examination is difficult and requires many years of practice, but once mastered, can provide a great deal of information about the CNS.

Oculomotor (III), Trochlear (IV), and Abducens (VI) Nerves

These nerves are examined together since they have similar functions. There are three parts to the examination of these nerves: pupillary light response, ocular movements and ptosis evaluation.

A. Pupillary Light Response: Pupillary size depends on the balance between the parasympathetic nervous system which causes constriction via CN III, and the sympathetic nervous system which causes dilation via the sympathetic pathway. When the examiner shines a light into the patient’s eye, that information travels through the optic chiasm and into both optic tracts to the pretectal nucleus in the midbrain. From here, the parasympathetic portions of both CN III nuclei (the Edinger-Westphal nucleus) are stimulated, the contralateral nucleus via the posterior commissure. These parasympathetic fibers travel with the 3rd nerve and constrict the pupil via the ciliary ganglion. Notice that equal constriction of both pupils should occur when shining the light into one eye. Notice that the pupillary light reflex assesses both CN II and CN III.

Posterior commissure

Looking to the nose is called accommodation and also results in pupillary constriction but via a pathway that comes from the occipital lobe. Since this pathway supplies the pretectal nucleus separately from the pupillary light reflex, a lesion that invades the pretectal area may disrupt the pupillary light response without disrupting pupillary constriction during accommodation. This is known as the Argyll-Robertson pupil and can occur with any pretectal nucleus lesion such as neurosyphilis. “The pupil accommodates but does not react.”

The sympathetic pathway for pupillary dilation is as follows:

• 1st order neuron: hypothalamus → brain stem → T1-T2 intermediolateral cell column • 2nd order neuron: T1-T2 intermediolateral cell column → white rami of nerve roots T1-T2 (over the apex of the lung) → cervical sympathetic chain → superior cervical ganglia • 3rd order neuron: superior cervical ganglia → on the surface of the carotid artery → Nasociliary branch of the 5th nerve → pupil dilator. The 3rd order neuron also supplies Muller’s muscle (eyelid elevation).

• A lesion anywhere in this sympathetic pathway may cause a Horner’s syndrome: mild ipsilateral pupillary constriction (miosis) and mild ipsilateral ptosis (drooping of the eyelid).

As you can see, the sympathetic innervation of the pupil is quite complicated, yet important to understand. A lesion anywhere in this pathway may cause Horner’s syndrome: mild ipsilateral pupillary constriction (miosis) and mild ipsilateral ptosis. If the lesion is proximal to the superior cervical ganglion, decreased ipsilateral sweating (anhydrosis) may also be present due to interruption of sympathetic fibers which supply the blood vessels and sweat glands of the face.

Some of the more common causes of a Horner’s syndrome include:

• 1st order lesion: brain stem stoke or hemorrhage, and cervical spinal cord trauma or demyelination • 2nd order lesion: apical lung tumor (a Pancoast tumor) a common board question • 3rd order lesion: carotid artery dissection, and some migraine headache variants

B. Ocular Movements: Ocular movements are assessed by having the patient follow the examiners finger in space, typically in an “H” pattern. Cranial nerves III, IV, and IV, control the eye movements by acting on six muscles:

III – Medial rectus, inferior oblique, inferior rectus, superior rectus IV – Superior oblique VI – Lateral rectus (Remember SO4, LR6)

The action of the superior oblique muscle is: - Primary gaze: incyclotorsion and depression - Abduction: incyclotorsion - Adduction: depression

Since adduction of the eye (i.e. – looking to the nose) aligns the eye with the axis of the superior oblique muscle, depression to the nose (“down and in”) is the strongest action of the superior oblique, followed by intorsion (or “incyclotorsion”) to the nose when the eye is abducted.

Confusion often arises about the SO function as some anatomy texts list the action as down and out. My understanding is that anatomists are describing the theoretical action of the SO acting in isolation (in a cadaver). Eye muscles work together, however, not independently. This, as well as the fact that the muscles have a stronger action when stretched, results in eye muscles that have a different vector when working as part of a unit. For example, the superior rectus (SR) when the eye is adducted is short and generates little force except for incyclotorsion; when the eye is abducted, however, the muscle is stretched and results in its strongest action to elevate the eye. Likewise, the

SO muscle is also stretched tightest when the eye is adducted. For the drawing below, you are looking on top of the eye for the superior muscles, from the bottom of the eye for the inferior muscles.

• A lesion of cranial nerve III (a 3rd nerve palsy) causes the eye to be deviated down and out (due to the unopposed pull of the lateral rectus), with associated ptosis (due to the loss of the levator palpebrae), and mydriasis.

Not show on the drawing above, but when this patient looks to the left, intorsion (incyclotorsion) movement of the right eye would be seen, indicating normal function of the superior oblique (4th nerve) muscle.

• A lesion of cranial nerve VI causes inward deviation of the eye (due to the unopposed pull of the medial rectus).

• Increased intracranial pressure will often result in dysfunction of both 6th nerves as seen below:

• A lesion of cranial nerve IV results in vertical diplopia. Patients say that walking down stairs or reading is difficult, which reflects the action of the superior oblique muscle. Tilting the head to the opposite shoulder minimized the diplopia.

In the picture below, notice that when the child looks straight ahead (B), the left eye is slightly higher (hypertropia). When the child tilts the head to the right, the eyes are now symmetrical (A). When looking to the right (C), the right eye cannot look down and in and so is pulled up. When tilting the head to the left (D), since the left eye cannot intort toward the nose, the left eye is higher.

The patient below has a left 4th nerve palsy. • In primary gaze there is very subtle hypertropia of the left eye:

• When looking to the right, the left eye goes up because of loss of down and in function:

• When looking both up and down, the loss of downward pull on the left eye again results in hypertropia:

• Tilting the head to the right results in conjugate gaze because the left eye is able to excyclotort normally:

• Tilting the head to the left, however, results in marked dysconjugate gaze because the left eye can’t incyclotort:

There are three types of conjugate eye movements detailed below:

Ocular movements that fixate the image on the retina:

 Vestibulo-Ocular Reflex: This reflex fixates the image on the retina with respect to head and neck motion. Head rotation is a form of angular acceleration that stimulates the semicircular canals in the inner ear. These canals convey angular acceleration into electrical impulses which then are conveyed to the four vestibular nuclei in the brain stem and then to CN’s III, IV, and VI with the MLF. This reflex is exploited in the evaluation of unconscious patients, where a normal VOR suggests that the brain stem is probably intact, and that the cause for the coma does not lie in the brain stem (see the vestibular and coma lectures later in the course). One type of VOR is the oculocephalic or “doll’s eyes” test where the eyes move in the opposite direction that the head is turned:

 Visual Pursuit: This reflex fixates the image on the retina with respect to image motion. Image motion is sensed by the occipital cortex which then relays this information in both a crossed and uncrossed manner to the lateral gaze center in the pons (the paramedian pontine reticular formation {PPRF}), and then via the MLF to CN’s III, IV, and VI.

Ocular movement that re-direct the line of sight:

 Visual Saccade: The stimulus for this ocular movement originates in the frontal eye fields (saccadic gaze center) in the frontal lobes. The information then travels down the anterior limb of the internal capsule and then crosses to eventually activate the opposite lateral gaze center, the paramedian pontine reticular formation (PPRF), in the pons. From here, the ipsilateral VI and contralateral III are activated, the latter by the medial longitudinal fasciculus (MLF) pathway.

For the most part, when you are asked about the MLF, it will be in reference to the connection between the PPRF and the part of the III nerve nucleus that controls the medial rectus muscle.

Clinical correlations of the above pathway (more will be added in the 2nd year neuroscience course):

• A cortical lesion that involves the saccadic gaze center (middle cerebral artery territory) results in a gaze preference, where the eyes look away from the hemiplegia.

• An extensive pontine lesion can result in a gaze palsy, where the patient looks at the hemiplegia limbs.

• A lesion involving the MLF results in an internuclear ophthalmoplegia (INO). Patients with an INO have weakness of the ipsilateral medial rectus muscle. Often there is associated nystagmus in the “normal” eye as the brain tries to correct for the diplopia. An MLF lesion in a young patient is virtually diagnostic of multiple sclerosis. Interestingly, patients with MLF lesions are able to adduct their eyes normally when looking to the nose since this eye movement requires a separate pathway.

During eye movement testing, the patients should also be observed for nystagmus, which is a rhythmic, oscillatory involuntary movement of one or both eyes that may occur spontaneously or be evoked by a specific direction of gaze. Nystagmus may be horizontal, vertical or rotatory, and typically has a fast and slow component. Arbitrarily, the direction of nystagmus is named by the direction of the fast component. Nystagmus may be physiologic (seen in normal patients) or pathologic, as noted in the list below.

Causes of Nystagmus

Physiologic Pathologic End-position Vestibular lesions Optokinetic Cerebellar lesions Caloric Brain stem lesions Drugs (phenytoin) Congenital

Trigeminal Nerve (V)

A. Sensory Examination: Each of the three divisions of the cranial nerves should be tested separately for touch, temperature, and pinprick sensation.

B. Corneal Reflex: The corneal reflex is tested by touching the cornea with a wisp of cotton while observing for any asymmetry of the blink response. Normally, both eyes blink symmetrically. The ophthalmic division of CN V provides the sensory of the cornea, while eye closure is accomplished by CN VII. Impulses from the spinal trigeminal nucleus reach the facial nucleus via interneurons in the reticular formation. The corneal reflex therefore is an excellent test of both cranial nerves V and VII.

C. Motor Examination: The temporalis, masseter, and lateral and medial pterygoids are all assessed. This is done by testing jaw closure, jaw opening, and side-to-side jaw movements. These muscles are all innervated by the mandibular division of the trigeminal nerve. ¡ jaw closure (medial pterygoid, masseter, temporalis), ¡ jaw opening (lateral pterygoids), ¡ side-to-side jaw movements (contralateral lateral > medial pterygoid)

D. The Jaw Jerk reflex: This involves tapping the chin with the mouth slightly open. This activates trigeminal sensory fibers which then stimulate trigeminal motor fibers to so that the mouth closes. Thus, this test assesses both trigeminal motor and sensory pathways.

Finally, when we discuss headache later in the course, it is relevant to known the meningeal innervation as supplied by the trigeminal nerve.

• The falx cerebri and cerebellar tentorium are supplied by V1 • The anterior and middle fossa and the meninges are supplied by the V2 and V3 • The posterior fossa and meninges are supplied by the C1-3 nerve roots.

Facial Nerve (VII)

A. Motor Examination: The major portions of this nerve can be tested by asking the patient to wrinkle the forehead, close the eyes tightly, smile and frown.

• A lower motor neuron lesion of the facial nerve (Bell’s palsy for example) or of the facial nucleus in the brain stem results in weakness of both the forehead and face. An upper motor neuron lesion that involves the cerebral cortex or of the corticobulbar pathway that connects the cortex with the facial nerve nucleus, results in weakness mainly of the lower half of the face. This occurs since the forehead receives bilateral cortical innervation.

The patient has a left Bell’s palsy. Notice the loss of wrinkles of left forehead due to frontalis muscle weakness and also that the left eye is open wider. The lower face is weak as well.

Over time, aberrant regeneration () may occur. For example, nerve fibers from the orbicularis oris muscle may regrow to supply the orbicularis oculi instead so that when the patient tries to purse their lips the eye squints. Another example of this occurs where fibers from the salivary glands are misdirected to the lacrimal gland resulting in “crocodile tears” stimulated by the smell or taste of food.

B. Taste: The facial nerve supplies taste sensation to the anterior 2/3 of the tongue. Taste can be checked by applying sugar or salt solutions to the anterior tongue with a cotton applicator.

Vestibulocochlear Nerve (VIII)

A. Cochlear Division: This can be tested rather crudely by assessing the patient’s ability to hear a ticking watch or by rubbing two fingers held at a certain distance from the ear.

• Hearing loss is frequently differentiated into conductive hearing loss (a lesion to the structures in the outer or middle ear which convert air conduction into bone conduction), and sensori-neural hearing loss (a lesion of the inner ear, or of CN VIII).

Two simple bedside tests are used to distinguish between these two types of hearing loss: the Weber test, and the Rinne test.

• In the Weber test, a vibrating tuning fork is placed at the vertex of the skull, and the patient is asked to localize the sound. Normally the sound should be equally heard in both ears. Lateralization to one ear is abnormal, with sound localizing to the “bad ear” in a conductive hearing loss and to the “good ear” in a sensori-neural hearing loss.

• In the Rinne test, the base of a vibrating tuning fork is placed against the mastoid process until the sound is not longer heard. The prongs of the tuning fork are then moved adjacent to the external ear where sound should still be appreciated, since air conduction (AC) is normally better than bone conduction (BC). If the sound is no longer heard in this second position, a conductive hearing loss is suspected. In sensori-neural hearing loss, both air and bone conduction are diminished although the normal relationship is maintained (AC is greater than BC).

Clinical Tests of Air Conduction (AC) and Bone Conduction (BC)

Test Normal Response Conductive HL Sensori-neural HL Weber No lateralization Lateralizes to defective ear Lateralizes to normal ear Rinne AC>BC BC>AC AC>BC, but both ↓

B. Vestibular Division: This nerve should be evaluated in patients complaining of dizziness or vertigo. The Vestibulo-Ocular Reflex (VOR) and the interaction between the vestibular nuclei and the control of eye movements were discussed in the section of CN’s III, IV, and VI. One way to test his reflex is to have the patient read a standard Snellen chart while the head is rotated back and forth. Deterioration of acuity by more than one line indicated an abnormality of the VOR. Other means of evaluating the vestibular nerve includes checking for nystagmus.

Labyrinthine stimulation can be performed by means of the Dix-Hallpike positioning maneuver, shown below. In this test, the patient is quickly moved from the sitting position to the supine position with the head 45º below the plane of the table and turned to one side. This position is maintained for about one minute, during which time the patient is observed for nystagmus. The test is then repeated with the head turned to the other side. If the patient reports vertigo during the maneuver, or if nystagmus develops, vestibular dysfunction may be present.

Caloric testing is an alternative way to stimulating the labyrinth. In this test, hot or cold water is introduced into the external auditory meatus and the patient is observed for the development of nystagmus or eye movements. This test is primarily used in comatose patients, and is another means of testing the brain stem in an unresponsive patient.

Glossopharyngeal (IX) and Vagus (X) nerves:

These nerves are usually tested together since they have overlapping functions. The glossopharyngeal nerve primarily carries sensation from the posterior pharynx and the larynx. The vagus nerve supplies motor innervation to the soft palate, pharyngeal muscles, and the vocal cords. The vagus nerve is easily tested by asking the patient to phonate and observing for a symmetrical rise in the palate and uvula.

The Gag Reflex is one means of assessing these nerves. The examiner touches the posterior pharyngeal wall with a tongue blade and observes for a symmetric rise in the soft palate and uvula. Touching the pharyngeal wall stimulates CN IX, which carries this information to CN X, which then causes the contraction of the soft palate. Another helpful and practical test is to observe the patient drinking a glass of water.

• An abnormality of these cranial nerves will result in dysphagia (swallowing difficulty).

Terminology: *Aphasia = A language abnormality * Dysarthria = A speech abnormality * Dysphagia = A swallowing abnormality

Spinal Accessory Nerve (XI):

The spinal Accessory nerve supplies motor innervation to the sternocleidomastoid muscle (SCM) and the upper trapezius. SCM function is assessed by asking the patient to rotate the head against resistance. Recall that contraction of the right SCM muscle allows one to turn the head to the left. Trapezius function is assessed by the shoulder shrug.

Hypoglossal Nerve (XII):

This nerve supplies motor innervation to the tongue. The patient is asked to protrude the tongue or push into the cheek against resistance.

• A lesion of one hypoglossal nerve causes the tongue to deviate towards the side of the injured nerve. A lesion of the UMN pathways that controls the hypoglossal nerve (the corticobulbar tract) can occasionally result in deviation of the tongue away from the lesion. More often, however, the UMN innervation of the hypoglossal nucleus is bilateral and the tongue does not deviate.

Cranial Nerve Reflexes: Summary

Reflex Afferent Nerve Efferent Nerve Pupillary II III Jaw Jerk V V Corneal V VII Gag IX X Vestibuloocular VIII III, IV, VI

4. Motor Examination

A. Muscle Strength: Muscle strength is quantified as much as possible by a 5 point scale:

Grade Muscle Strength 0 No Movement 1 Flicker of contraction 2 Full range of motion (ROM) with gravity eliminated 3 Full ROM against gravity 4 Full ROM against gravity and offers some resistance 5 Full Power

Since there is such a vast range of weakness between a 4/5 and a 5/5, most neurologists use 4+ or 5- to the scale.

It is also useful to assess functional motor strength where the patient is instructed to perform certain tasks (raise arms above the head, stand on toes, deep knee bends, etc.). Two of the more important functional tests are finger tapping and the . The pronator drift is performed by having the patient hold both hands outstretched with the palms up and the eyes closed. The examiner watches for subtle pronation of the arm. Both abnormal finger tapping and pronation of the arm are sensitive indicators of an UMN injury. Finger tapping is also a useful test for assessing the basal ganglia and the cerebellum.

The most important upper motor neuron (UMN) pathway is the corticospinal tract. This pathway begins in the frontal lobe, crosses sides in the lower medulla, and eventually ends up “talking” to anterior horn cells in the contralateral spinal cord. In this way, the right brain controls motor function on the left side of the body.

• This means that a lesion that affects the right brain (such as a stroke) may lave the left arm and leg weak. A lesion of the right spinal cord (such as a herniated disc) will leave the right side of the body below the level of the lesion weak, since the corticospinal tract has already crossed in the medulla. There are many other UMN pathways that will be covered later in the course.

B. Muscle Tone: Muscle tone is the resistance of a muscle to passive stretching. Tone may be increased in various pathological states, as follows:

Exam Description Pathology Spasticity (clasp knife) → Has a catch which varies with UMN lesion Position and is velocity dependent Rigidity (lead pipe) → Steady resistance to movement Basal Ganglia lesion (not velocity dependent) (Parkinson’s disease) Paratonia → Inability to relax the muscle Bihemispheric lesion (Alzheimer’s disease)

C. Muscle Bulk: Loss of muscle bulk is known as atrophy, and is seen in two main pathological settings:

• Denervation atrophy: A profound form of muscle atrophy that is seen with lower motor neuron lesion • Disuse atrophy: A mild form of muscle atrophy that can be seen in many clinical settings, including UMN lesions, casting, etc.

D. Abnormal Spontaneous Movements

• : Worm-like contractions of muscle due to a random discharge of an entire motor unit. These are usually benign, but are also seen in diseases of the lower motor neuron, especially those that involve the anterior horn cells (amyotrophic lateral sclerosis, and polio – see later description of these conditions)

• Movement Disorders: These are too vast to cover in this lecture, but most of these are due to pathology in the basal ganglia. For example, a rest is commonly seen in Parkinson’s disease (substantia nigra degeneration). Chorea (brief, irregular, writhing movements) is seen in diseases such as Huntington’s disease (striatum degeneration).

5. Sensory Examination

Pain and Temperature Pathways (Protopathic sensation): A new safety pin should be used and discarded after the single examination. Pain is carried by small unmyelinated fibers. Temperature can be assessed with a cool tuning fork. Upon reaching the spinal cord, these fibers cross within a level or two and ascend in the contralateral spinal cord (i.e. pain fibers form the left leg ascend to the brain in the right spinal cord). This pathway is known as the spinothalamic tract. This pathway synapses in the ventral posterior lateral (VPL) nucleus of the thalamus prior to terminating in the post-central gyrus.

Vibration and Proprioception Pathways (Epicritic Sensation): These modalities are carried by large, myelinated fibers. Vibration is assessed using a tuning fork (128 Hz) applied over a distal joint. If vibratory sensation is absent distally, more proximal joints are assessed. Proprioception is evaluated by assessing position sense at interphalangeal joints with slight degrees of motion. The examiner grasps the patient’s joint laterally so as not to provide pressure clues.

Unlike the Spinothalamic tract, when these fibers reach the spinal cord, they ascend in the ipsilateral spinal cord (i.e. vibratory sensation from the left leg ascends in the left spinal cord). This pathway is sometimes called the posterior columns, because they travel in the posterior portion of the spinal cord. This pathway also relays in the VPL prior to arriving in the post-central gyrus.

Another means of assessing posterior column function is the Romberg test. This test is performed by asking the patient to stand with his/her feet together and then close the eyes. The patient is then observed to see if balance can be maintained. The test is positive if the patient falls to one side (of course, you don’t let the patient fall!).

Three systems are routinely used to maintain balance, namely proprioception, the vestibular apparatus, and vision. Only two of these systems are required at any one time. Eye closure removes visual cues for maintaining balance. If balance is maintained with the eyes closed, this implies integrity of both the vestibular apparatus and proprioception. Falling to one side implies dysfunction of one of these balance systems (proprioception or vestibular).

The Romberg test can only be performed if the patient is able to stand well with feet together and eyes open. If the patient cannot do this well, the Romberg test cannot be performed.

• Peripheral Neuropathies are disease of the peripheral nerves. Most peripheral neuropathies affect mainly the pain and temperature fibers, although some neuropathies preferentially involve the large fibers that carry vibratory and proprioceptive information.

6. Cerebellar Function

The cerebellum coordinates movement. Coordination testing is divided into two parts: truncal stability, and limb coordination. Diseases or lesions of the cerebellum result in poor coordination of voluntary movement, or (not weakness).

A. Truncal Stability: This is accessed by observing the patients balance when sitting, standing or walking.

• Truncal ataxia suggests a midline cerebellar (vermis) lesion, such as occurs with chronic alcohol abuse.

B. Limb Coordination: The patient is asked to touch his/her nose with the index finger, then the examiner’s finger, and then back to his/her nose (the finger-to-nose test). In the lower extremity, the patient is asked to slide one heel down the opposite shin (the heel-to- shin test).

• Ataxia of these limb movements indicates a lesion in the cerebellar hemisphere. Unlike the cerebral cortex (the brain) in which one hemisphere controls the opposite side of the body, one cerebellar hemisphere controls the same side of the body (the right cerebellum coordinates the right arm and leg). Therefore, ataxia of the right arm and leg indicates a lesion of the right cerebellum.

Below is an example of an ataxic finger to nose test.

7. Reflexes

A. Muscle Stretch Reflexes (sometimes called deep tendon reflexes or DTR’s):

Muscle stretch reflexes are monosynaptic spinal cord reflexes that are elicited by striking the muscle tendon with a percussion hammer and evaluating the subsequent contraction of the muscle. Striking the muscle tendon stretches the muscle spindle and this afferent information is carried by the afferent sensory nerve fibers through the dorsal root and dorsal horn of the spinal cord, eventually synapsing on a corresponding anterior horn cell in the ventral horn of the spinal cord. The efferent arm of this reflex originates in the anterior horn cell, exits the spinal cord in the ventral root, and eventually synapses on the same muscle.

Five muscle stretch reflexes are commonly assessed.

Reflex Nerve Root Achilles S 1-2 Patellar L 2-4 Brachioradialis C 5-6 Biceps C 5-6 Triceps C 6-8

Reflexes are graded as follows:

Grade Description 0 Absent (may be normal but suggests LMN lesion) 1 Hypoactive 2 Normal 3 Hyperactive 4 Hyperactive with clonus (always abnormal due to UMN lesion)

• Clonus is a rhythmic series of involuntary muscle contractions induced by the sudden passive stretching of a muscle. It is most easily elicited at the ankle. It indicates an UMN lesion.

B. The Babinski Sign (extensor plantar response): This is performed by striking the lateral aspect of the sole of the foot with a painful stimulus, starting at the heel and then crossing the ball of the foot towards the great toe. Normally the toe goes down or does not move.

• An abnormal (positive) Babinski response consists of dorsiflexion of the great toe (it goes up). This is indicative of an UMN lesion.

C. Frontal Release Signs are reflexes that are present in infancy, lost with maturation of the central nervous system, and regained with advanced age or with diffuse cortical or bihemispheric dysfunction, such as can be seen with Alzheimer’s disease or bihemispheric strokes. Four frontal release signs are commonly tested: snout, palmomental, grasp, and glabellar reflexes.

• Snout Reflex: This is elicited by repeatedly tapping the upper lip and observing for puckering of the lips. One way of eliciting this reflex is to place a tongue blade lightly over the upper lip and then tap the tongue blade with a percussion hammer.

• Palmomental Reflex: This is elicited by scratching the thenar eminence of the palm with a blunt object and observing for an ipsilateral contraction of the mentalis muscle on the chin.

• Grasp Reflex: This is obtained by having the examiner stroke the skin of the patient’s palm with his/her fingers and observing for a resultant grasping of those fingers by the patient.

• Glabellar Sign: This elicited by tapping the forehead repeatedly between the eyebrows over the glabella and observing for persistent blinking. It is important to note that a normal individual will blink once or twice only with this maneuver.

8. Gait

Examination of the gait is very important in neurology, since it provides invaluable information concerning integrity of the motor system, sensory system, and cerebellum. Gait is assessed while watching the patient walk normally. Making the gait more difficult by having the patient walk on his/her toes and heels, including tandem gait (heel-to-toe walking) is also performed.

Various gait abnormalities are as follows:

Gait Lesion Asymmetric Trendelenburg Hip pathology or gluteus medius weakness Hemiplegic UMN lesion (stroke) Steppage Peroneal nerve palsy Antalgic Foot or leg pain Symmetric Wide based: Sensory ataxic Posterior columns Cerebellar ataxic Cerebellum Narrow based: Spastic (scissored gait) Bilateral UMN (cerebral palsy) Festinating (shuffled gait) Basal Ganglia (Parkinson’s disease)

Lesion Localization

When a patient presents with motor weakness, it is often helpful to determine if the weakness is due to an upper motor neuron lesion or to a lower motor neuron lesion. The following table lists several motor and reflex findings that can help one make such a determination.

Differentiation between UMN and LMN Lesions Reflexes Babinski Tone Weakness Atrophy Fasciculations UMN ↑ ↑ (toe up) ↑ Spastic - (mild) - LMN ↓ ↓ ↓ Flaccid + +