Brainstem Anatomy, Surgical Procedures and Cranial

SECTIONS OF THE BRAINSTEM ANATOMY, SURGICAL BRAINSTEM PROCEDURES AND CRANIAL NERVE MONITORING Thalamus James Watt, BS, CNIM, R.EP.T Midbrain MSET 2017 Pons

Medulla Oblongata

CRANIAL NERVES 1. OLFACTORY NERVE

1. Olfactory 7. Facial

2. Optic 8. Vestibulocochlear • Sensory

3. Oculomotor 9. Glossopharyngeal • Not monitored during surgery

4. Trochlear 10.Vagus • Origin - Telencephalon Trigeminal Spinal Accessory 5. 11. • Nuclei - Anterior olfactory nucleus 6. Abducens 12.Hypoglossal

THE BIG PICTURE THE BIG PICTURE Optic Canal - II Superior Orbital Fissure - III, IV, V1 and V(1) Foramen Rotundum - V(2) Foramen Ovale - V(3) Internal Acoustic Meatus - VII & VIII Jugular Foramen - IX, X, XI Hypoglossal Canal - X THE BIG PICTURE THE BIG PICTURE Optic Canal - II Optic Canal - II Superior Orbital Fissure - III, IV, V1 and V(1) Superior Orbital Fissure - III, IV, V1 and V(1) Foramen Rotundum - V(2) Foramen Rotundum - V(2) Foramen Ovale - V(3) Foramen Ovale - V(3) Internal Acoustic Meatus - VII & VIII Internal Acoustic Meatus - VII & VIII Jugular Foramen - IX, X, XI Jugular Foramen - IX, X, XI Hypoglossal Canal - X Hypoglossal Canal - X

THE BIG PICTURE THE BIG PICTURE Optic Canal - II Optic Canal - II Superior Orbital Fissure - III, IV, V1 and V(1) Superior Orbital Fissure - III, IV, V1 and V(1) Foramen Rotundum - V(2) Foramen Rotundum - V(2) Foramen Ovale - V(3) Foramen Ovale - V(3) Internal Acoustic Meatus - VII & VIII Internal Acoustic Meatus - VII & VIII Jugular Foramen - IX, X, XI Jugular Foramen - IX, X, XI Hypoglossal Canal - X Hypoglossal Canal - X

• Mainly motor

• Spontaneous and triggered • Sensory EMG monitored during • Monitored using Flash Visual Evoked surgery Potentials during surgery • Origin - Anterior aspect of • Origin - Retina Midbrain • • Nucleus - Lateral geniculate nucleus Nucleus - Oculomotor nucleus, Edinger-Westphal nucleus

3. OCULOMOTOR 3. OCULOMOTOR

• Mainly motor • Mainly motor

• Spontaneous and triggered • Spontaneous and triggered EMG monitored during EMG monitored during surgery surgery

• Origin - Anterior aspect of • Origin - Anterior aspect of Midbrain Midbrain

• Nucleus - Oculomotor • Nucleus - Oculomotor nucleus, Edinger-Westphal nucleus, Edinger-Westphal nucleus nucleus

3. OCULOMOTOR 3. OCULOMOTOR

• Mainly motor • Mainly motor

• Spontaneous and triggered • Spontaneous and triggered EMG monitored during EMG monitored during surgery surgery

• Origin - Anterior aspect of • Origin - Anterior aspect of Midbrain Midbrain

• Nucleus - Oculomotor • Nucleus - Oculomotor nucleus, Edinger-Westphal nucleus, Edinger-Westphal nucleus nucleus 3. OCULOMOTOR 3. OCULOMOTOR

• Mainly motor • EMG monitored from • Spontaneous and triggered EMG monitored during • Inferior Rectus Muscle surgery • Nerve also innervates • Origin - Anterior aspect of • Superior Rectus Muscle Midbrain • Medial Rectus Muscle • Nucleus - Oculomotor nucleus, Edinger-Westphal • Inferior Oblique Muscle nucleus

3. OCULOMOTOR 4. TROCHLEAR NERVE

• EMG monitored from

• Inferior Rectus Muscle • Motor

• Nerve also innervates • Spontaneous and triggered EMG monitored during surgery • Superior Rectus Muscle • Origin - Dorsal aspect of Midbrain • Medial Rectus Muscle • Nucleus - Trochlear nucleus • Inferior Oblique Muscle Yingling

4. TROCHLEAR NERVE 4. TROCHLEAR NERVE

• Motor • Motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Dorsal aspect of Midbrain • Origin - Dorsal aspect of Midbrain

• Nucleus - Trochlear nucleus • Nucleus - Trochlear nucleus 4. TROCHLEAR NERVE 4. TROCHLEAR NERVE

• Motor • Motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Dorsal aspect of Midbrain • Origin - Dorsal aspect of Midbrain

• Nucleus - Trochlear nucleus • Nucleus - Trochlear nucleus

4. TROCHLEAR NERVE 4. TROCHLEAR NERVE

• EMG monitored from • EMG monitored from

• Superior Oblique Muscle • Superior Oblique Muscle

Yingling

6. ABDUCENS NERVE 6. ABDUCENS NERVE

• Mainly Motor • Mainly Motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - ﬂoor of the fourth ventricle in • Origin - ﬂoor of the fourth ventricle in the Pons the Pons

• Nucleus - Abducens nucleus • Nucleus - Abducens nucleus 6. ABDUCENS NERVE 6. ABDUCENS NERVE

• Mainly Motor • Mainly Motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - ﬂoor of the fourth ventricle in • Origin - ﬂoor of the fourth ventricle in the Pons the Pons

• Nucleus - Abducens nucleus • Nucleus - Abducens nucleus

6. ABDUCENS NERVE 6. ABDUCENS NERVE

• Mainly Motor

• Spontaneous and triggered EMG monitored during surgery • EMG monitored from

• Origin - ﬂoor of the fourth ventricle in • Lateral Rectus Muscle the Pons

• Nucleus - Abducens nucleus

6. ABDUCENS NERVE EYE MOVEMENTS

• EMG monitored from

• Lateral Rectus Muscle

Yingling 5. TRIGEMINAL NERVE 5. TRIGEMINAL NERVE

• Mixed Sensory and Motor • Mixed Sensory and Motor

• Motor component monitored during • Motor component monitored during surgery using spontaneous and triggered surgery using spontaneous and triggered EMG EMG

• Sensory component monitored using • Sensory component monitored using trigeminal SEPs and blink reﬂex trigeminal SEPs and blink reﬂex

• Origin - Pons • Origin - Pons

• Nucleus - Trigeminal nucleus • Nucleus - Trigeminal nucleus

5. TRIGEMINAL NERVE 5. TRIGEMINAL NERVE

• Mixed Sensory and Motor • Mixed Sensory and Motor

• Motor component monitored during • Motor component monitored during surgery using spontaneous and triggered surgery using spontaneous and triggered EMG EMG

• Sensory component monitored using • Sensory component monitored using trigeminal SEPs and blink reﬂex trigeminal SEPs and blink reﬂex

• Origin - Pons • Origin - Pons

• Nucleus - Trigeminal nucleus • Nucleus - Trigeminal nucleus

5. TRIGEMINAL NERVE 5. TRIGEMINAL NERVE

• Mixed Sensory and Motor • Mixed Sensory and Motor

• Motor component monitored during • Motor component monitored during surgery using spontaneous and triggered Superior Orbital Fissure surgery using spontaneous and triggered EMG EMG Foramen Rotundum • Sensory component monitored using • Sensory component monitored using trigeminal SEPs and blink reﬂex trigeminal SEPs and blink reﬂex Foramen Ovale • Origin - Pons • Origin - Pons

• Nucleus - Trigeminal nucleus • Nucleus - Trigeminal nucleus 5. TRIGEMINAL NERVE 5. TRIGEMINAL NERVE

• Mixed Sensory and Motor

• Motor component monitored during surgery using spontaneous and triggered EMG

• Sensory component monitored using trigeminal SEPs and blink reﬂex

• Origin - Pons V1 - Opthalmic V2 - Maxillary V3 - Mandibular • Nucleus - Trigeminal nucleus

5. TRIGEMINAL NERVE 7. FACIAL NERVE

• Mixed sensory and motor

• EMG monitored from muscles of • Motor component monitored using mastication spontaneous and triggered EMG monitored during surgery • Temporalis • Origin - Cerebellopontine angle • Masseter • Nucleus - Facial nucleus, solitary nucleus, superior salivary nucleus

7. FACIAL NERVE 7. FACIAL NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Cerebellopontine angle • Origin - Cerebellopontine angle

• Nucleus - Facial nucleus, solitary nucleus, • Nucleus - Facial nucleus, solitary nucleus, superior salivary nucleus superior salivary nucleus 7. FACIAL NERVE 7. FACIAL NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Cerebellopontine angle • Origin - Cerebellopontine angle

• Nucleus - Facial nucleus, solitary nucleus, • Nucleus - Facial nucleus, solitary nucleus, superior salivary nucleus superior salivary nucleus

7. FACIAL NERVE 7. FACIAL NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Cerebellopontine angle • Origin - Cerebellopontine angle

• Nucleus - Facial nucleus, solitary nucleus, • Nucleus - Facial nucleus, solitary nucleus, superior salivary nucleus superior salivary nucleus

7. FACIAL NERVE 7. FACIAL NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Cerebellopontine angle • Origin - Cerebellopontine angle

• Nucleus - Facial nucleus, solitary nucleus, • Nucleus - Facial nucleus, solitary nucleus, superior salivary nucleus superior salivary nucleus 7. FACIAL NERVE 7. FACIAL NERVE

• • Mixed sensory and motor EMG monitored from • • Motor component monitored using Temporal branch - Frontalis spontaneous and triggered EMG • Zygomatic branch - O.Oculi monitored during surgery • Buccal branch - O.Oris • Origin - Cerebellopontine angle • Mandibular Branch - Mentalis • Nucleus - Facial nucleus, solitary nucleus, superior salivary nucleus • Cervical Branch - Platysma

8. VESTIBULOCOCHLEAR NERVE 9. GLOSSOPHARYNGEAL NERVE

• Mixed sensory and motor • Sensory • Motor component monitored using • Monitored during surgery using spontaneous and triggered EMG during brainstem auditory evoked potentials surgery • Origin - Cerebellopontine angle • Origin - Medulla • Nucleus - Vestibular nucleus, cocnlear • Nucleus - Nucleus ambiguus, inferior nucleus salivary nucleus, solitary nucleus

9. GLOSSOPHARYNGEAL NERVE 9. GLOSSOPHARYNGEAL NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG during spontaneous and triggered EMG during surgery surgery

• Origin - Medulla • Origin - Medulla

• Nucleus - Nucleus ambiguus, inferior • Nucleus - Nucleus ambiguus, inferior salivary nucleus, solitary nucleus salivary nucleus, solitary nucleus 9. GLOSSOPHARYNGEAL NERVE 9. GLOSSOPHARYNGEAL NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG during spontaneous and triggered EMG during surgery surgery

• Origin - Medulla • Origin - Medulla

• Nucleus - Nucleus ambiguus, inferior • Nucleus - Nucleus ambiguus, inferior salivary nucleus, solitary nucleus salivary nucleus, solitary nucleus

9. GLOSSOPHARYNGEAL NERVE 9. GLOSSOPHARYNGEAL NERVE

• EMG monitored from • EMG monitored from

• Stylopharyngeus muscle of the soft • Stylopharyngeus muscle of the soft palate palate

10. VAGUS NERVE 10. VAGUS NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG during spontaneous and triggered EMG during surgery surgery

• Origin - Medulla • Origin - Medulla

• Nucleus - Nucleus ambiguus, dorsal • Nucleus - Nucleus ambiguus, dorsal motor vagal nucleus, solitary nucleus motor vagal nucleus, solitary nucleus 10. VAGUS NERVE 10. VAGUS NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG during spontaneous and triggered EMG during surgery surgery

• Origin - Medulla • Origin - Medulla

• Nucleus - Nucleus ambiguus, dorsal • Nucleus - Nucleus ambiguus, dorsal motor vagal nucleus, solitary nucleus motor vagal nucleus, solitary nucleus

10. VAGUS NERVE 10. VAGUS NERVE

• Mixed sensory and motor • Mixed sensory and motor

• Motor component monitored using • Motor component monitored using spontaneous and triggered EMG during spontaneous and triggered EMG during surgery surgery

• Origin - Medulla • Origin - Medulla

• Nucleus - Nucleus ambiguus, dorsal • Nucleus - Nucleus ambiguus, dorsal motor vagal nucleus, solitary nucleus motor vagal nucleus, solitary nucleus

10. VAGUS NERVE 10. VAGUS NERVE

• Branchial motor ﬁbers separate into three • Branchial motor ﬁbers separate into three major branches major branches

• Pharyngeal - innervates all muscles of • Pharyngeal - innervates all muscles of pharynx and soft palate excpt pharynx and soft palate excpt stylopharyngeus and tensor veli palatini stylopharyngeus and tensor veli palatini

• Superior laryngeal - innervates • Superior laryngeal - innervates cricothyroid muscle cricothyroid muscle

• Recurrent laryngeal - innervates intrinsic • Recurrent laryngeal - innervates intrinsic muscles of larynx muscles of larynx 10. VAGUS NERVE 10. VAGUS NERVE

• Branchial motor ﬁbers separate into three major branches • EMG monitored from • Pharyngeal - innervates all muscles of pharynx and soft palate excpt • Vocalis Muscle stylopharyngeus and tensor veli palatini • Monitored using endotracheal tube • Superior laryngeal - innervates cricothyroid muscle electrode or hookwires placed in vocalis muscle • Recurrent laryngeal - innervates intrinsic muscles of larynx

10. VAGUS NERVE 11. SPINAL ACCESSORY NERVE

• Mainly motor

• Spontaneous and triggered EMG monitored during surgery

• Origin - Cranial and cervical spinal roots

• Nucleus - Nucleus ambiguus, spinal accessory nucleus

11. SPINAL ACCESSORY NERVE 11. SPINAL ACCESSORY NERVE

• Mainly motor • Mainly motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Cranial and cervical spinal roots • Origin - Cranial and cervical spinal roots

• Nucleus - Nucleus ambiguus, spinal • Nucleus - Nucleus ambiguus, spinal accessory nucleus accessory nucleus 11. SPINAL ACCESSORY NERVE 11. SPINAL ACCESSORY NERVE

• Mainly motor • Mainly motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Cranial and cervical spinal roots • Origin - Cranial and cervical spinal roots

• Nucleus - Nucleus ambiguus, spinal • Nucleus - Nucleus ambiguus, spinal accessory nucleus accessory nucleus

11. SPINAL ACCESSORY NERVE 12. HYPOGLOSSAL NERVE

• Mainly motor • EMG monitored from • Spontaneous and triggered EMG • Trapezius muscle monitored during surgery • Origin - Medulla • Sternocleidomastoid muscle • Nucleus - Hypoglossal nucleus

12. HYPOGLOSSAL NERVE 12. HYPOGLOSSAL NERVE

• Mainly motor • Mainly motor

• Spontaneous and triggered EMG • Spontaneous and triggered EMG monitored during surgery monitored during surgery

• Origin - Medulla • Origin - Medulla

• Nucleus - Hypoglossal nucleus • Nucleus - Hypoglossal nucleus 12. HYPOGLOSSAL NERVE 12. HYPOGLOSSAL NERVE

• EMG monitored from • EMG monitored from

• Anterior 2/3 of tongue • Anterior 2/3 of tongue

• Innervates all muscles of tongue • Innervates all muscles of tongue except palatoglossus muscle except palatoglossus muscle

POSTERIOR FOSSA SURGICAL APPROACHES

• Transpetrosal Approach

• Retrolabyrinthine

• Translabyrinthine

• Transcochlear

RETROLABYRINTHINE TRANSLABYRINTHINE APPROACH APPROACH

• Indication - Small lesions of the anterior • Indication - Vestibular Schwannoma brainstem • Cranial 7 at risk, hearing sacriﬁced, • Cranial nerves 7 & 8 are at risk for possibly lower cranial nerves for larger injury, possibly lower cranial nerves for tumors larger lesions TRANSCOCHLEAR APPROACH TRANSCOCHLEAR APPROACH

• Increases surgical exposure for complex • Increases surgical exposure for complex lesions lesions

• Hearing sacriﬁced, cranial nerve 7 likely • Hearing sacriﬁced, cranial nerve 7 likely to sustain injury during procedure to sustain injury during procedure

RETROSIGMOID APPROACH TRANSPETROSAL APPROACHES

Surgical Approach Post-op Hearing Function Post-op Facial Function

Retrolabyrinthine Preserved Preserved • Cranial nerves 7 & 8 at risk, lower cranial nerves for larger tumors Translabyrinthine Sacriﬁced Preserved

Transient or permanent Transcochlear Sacriﬁced paralysis

FAR-LATERAL APPROACH TRANSORAL APPROACH

• Provides access to basilar and vertebral arteries • Provides access to anterior extradural • Provides access to lateral and anterior lesions brainstem • Upper cranial nerves at risk for injury • Decreases need for cerebellar retraction

• Lower cranial nerves at risk for injury ANESTHETIC REQUIREMENTS MONITORING TECHNIQUE

• Auditory Brainstem Evoked Response • Two triggered EMG techniques Motor Cranial Nerve EMG Monitoring Auditory Brainstem Response monitoring for brainstem and cochlear • Monitoring nerve function Monopolar stimulation - sensitive, • No muscle relaxants used as searching to locate cranial • Minimally effected by Propofol and • Monitor spontaneous EMG from motor nerves that may not be visible • No local anesthetics inhalation agents cranial nerves to detect nerve irritation because of tumor • • • Initial latency shift with induction Monitor triggered EMG from motor Bipolar stimulation - speciﬁc, used to cranial nerves to test nerve function test motor cranial nerve function • Avoid Nitrous Oxide and to detect neural ischemia during resection and to demonstrate that nerve is intact at completion of resection

STIMULATOR TYPES STIMULATOR TYPES

Monopolar Bipolar Monopolar

Yingling

BRAINSTEM AUDITORY EVOKED SPONTANEOUS AND TRIGGERED EMG RESPONSE MONITORING CAN INDICATE IMPENDING INJURY

• Brainstem retraction and cranial nerve manipulation can cause BAER to change

• Wave V amplitude and interpeak latencies most important indicator of change