Raised : What it is and how to recognise it This article presents an approach to raised intracranial pressure (ICP) constructed in a question-answer fashion. It is not intended to be a comprehensive review of a complex subject, but rather an ‘easy-access quick overview’ to provide practical information on the physiology, pathology and management of raised ICP for the busy practitioner.

D Roytowski, MB ChB, MBA (INSEAD) A Figaji, MB ChB, MMed, PhD, FCNeurosurg (SA) Division of , University of Cape Town and Institute for Child Health, Red Cross War Memorial Children's Hospital, Cape Town

Correspondence to: D Roytowski ([email protected])

What is raised intracranial using a manometer after . volume. Once the compensatory reserve is pressure? ICP varies over the course of the day exceeded the increase in pressure for a given Intracranial pressure (ICP) is the tension and is influenced by changes in posture, increase in volume will rise dramatically within the cranial vault. Typically recorded position and pressure fluctuations in other (Fig. 3). in millimetres of mercury (mmHg), ICP compartments (e.g. a Valsalva manoeuvre in adults is normally 5 - 10 mmHg, in will markedly increase the resting ICP). Why is ICP important? children 3 - 7 mmHg, and in infants 1.5 - Raised ICP can be defined in many ways, Raised ICP is the final common pathway 6 mmHg.[1] The mmHg value is multiplied but in the acute setting it commonly refers that leads to death or disability in most acute by 1.36 to determine the equivalent value to pressure greater than 20 - 25 mmHg for cerebral conditions. It is also potentially in cmH2O. This is usually obtained when more than 5 minutes. treatable. The two major consequences of increased ICP are: The is a rigid container with 3 key • brain shifts component constituents – brain tissue, • brain ischaemia. cerebral blood and

Mass (CSF). The Monro-Kellie doctrine states Cerebral perfusion pressure (CPP) is the that the sum of intracranial volumes is calculated difference between the mean constant and therefore an increase in any arterial pressure (MAP) and the ICP. CPP = Brain one of these compartments must be offset MAP – ICP. by an equivalent decrease in the other two CSF Blood (Fig. 1). Why is CPP important? The CPP is the main determinant of Under normal conditions the pressure within cerebral blood flow (CBF). Normally CBF is Skull the cranial space is in equilibrium. Should coupled to metabolic demand of tissue, with

Lumbar pressure from one constituent increase, normal flow greater than 50 ml/100 g/min. CSF compensation occurs (up to a point) by Less than 20 ml/100 g/min is considered reduction in volume of another constituent the ischaemic threshold. The process of Fig. 1. Representation of the cranial and a subsequent rise in ICP. This generally cerebral autoregulation maintains CBF constituents. involves shifts of CSF and venous blood out between a CPP range of approximately 50 of the cranium to compensate for the added - 150 mmHg.[2,3] Outside these ranges CBF volume. Once this compensatory reserve is becomes pressure-dependent. As shown exhausted, pressure increases and brain shifts in Fig. 4, when CPP is less than the lower may occur and result in herniation (Fig. 2). threshold for autoregulatory compensation, CBF progressively decreases with CPP, The compliance curve is expressed by resulting in ischaemia. plotting the ICP against an expanding Intracranial compliance curve What are the causes of raised ICP? Several conditions cause raised ICP, either by increasing one or more of the constituents of the intracranial cavity or by introducing ΔB a non-native mass to the cranial space (see Table 1). Intracranial pressure (ICP) pressure Intracranial ΔA Raised ICP is typically caused by one of the Fig. 2. Sites of brain herniation. 1: subfalcine; following four mechanisms: 2: transtentorial; 3: uncal (transtentorial); 4: Increase in intracranial volume • cerebral oedema (brain tissue) tonsillar. Fig. 3. Intracranial compliance curve. • vascular (congestive) brain swelling

85 CME March 2013 Vol. 31 No. 3 Raised intracranial pressure

• (CSF) without focal neurological signs or . Palsy of the 3rd cranial nerve tends • mass lesion. papilloedema. Therefore absence of the latter to be on the side of the lesion, whereas palsy does not exclude increased ICP. Meningism, of the 4th cranial nerve is non-localising. How do I recognise raised ICP? commonly associated with the meningeal The presenting circumstances, coupled with irritation of , may be mistaken The downward displacement of the a high degree of suspicion, should guide for neck stiffness associated with impending and upper cervical cord through the foramen efforts to diagnose raised ICP. However, it tonsillar herniation. A lumbar puncture under magnum causes compression on structures can be very difficult to conclusively exclude these circumstances could prove fatal. that control cardiac and respiratory function. raised ICP on clinical grounds, so delayed Critical compression may result in Cushing’s diagnoses and inappropriate management , vomiting and visual disturbances triad of increased systolic pressure (including are unfortunately common. Early diagnosis are common symptoms of raised ICP. widened pulse pressure), bradycardia and is important for several reasons: Diplopia may occur due to cranial nerve irregular breathing. • delay in diagnosis increases morbidity palsies – the 6th cranial nerve is particularly • inappropriate management (e.g. lumbar vulnerable to stretch while the 3rd cranial Several brain herniation syndromes have puncture) may worsen the condition. nerve is at risk because herniation of the been described.[5] Should the patient present medial through the tentorial with any of these, urgent consultation with a ICP varies over the course notch stretches the nerve as it exits the neurosurgeon is mandatory. of the day and is influenced by changes in posture, Table 1. Common pathologies that result in raised intracranial pressure[4] position and pressure Hydrocephalus Congenital or acquired Non-communicating or communicating fluctuations in other Brain tumour (primary or Secondary hydrocephalus (mass causing blockage of CSF compartments. secondary, benign or malignant) pathways) Mass effect Oedema The history should guide the clinician in assessing the risk of raised ICP, even in the CNS infections Meningitis absence of key neurological signs. Abscess Establish the patient’s level of Secondary hydrocephalus – the Glasgow Scale (GCS) is Mass effect widely used to reliably grade the level of Trauma Intracranial haematoma (extradural, subdural, consciousness (Table 2). Critically raised ICP intracerebral) causes a depressed level of consciousness Diffuse brain swelling and, depending on the cause, may require Cerebrovascular Subarachnoid haemorrhage emergent neurosurgical intervention. Keep Intracerebral haematoma in mind, however, that causes of chronically Intraventricular haemorrhage increased ICP may first present insidiously. Intracranial volume may increase steadily Secondary hydrocephalus over months with no change in the level of Venous thrombosis consciousness, and yet present dramatically Cerebral infarct with an acute deterioration of consciousness Hypertensive (malignant , when intracranial compliance is finally eclampsia) exhausted. Acutely increased ICP may present Metabolic encephalopathy Hypoxic-ischaemic with rapidly deteriorating consciousness Hepatic coma Cerebral autoregulation Renal failure Diabetic ketoacidosis 100 Near drowning 75 Hyponatraemia

50

Cerebral blood ow Cerebral Craniocerebral disproportion 25 Pressure dependent regions Developmental lesions 0 0 50 100 150 200 Epidermoid cyst Cerebral perfusion pressure Idiopathic intracranial hypertension Fig. 4. Cerebral autoregulation.

86 CME March 2013 Vol. 31 No. 3 Raised intracranial pressure

valuable in assessing the likelihood of raised ICP. Several symptoms and signs have been described: • Visual obscurations are transient losses of vision lasting a few seconds, occurring with raised ICP, particularly when associated with activities that increase ICP (coughing, sneezing, bending down, straining at stool) and relieved by their cessation. These symptoms are thought to reflect critical compromise of optic nerve head perfusion and are typically associated Normal scan Swollen brain Extradural haematoma with the finding of papilloedema. • Retinal venous pulsation is evident at the margin of the disc in the normal retina when observed with an ophthalmoscope. Venous pulsation is lost when ICP exceeds venous pressure. This is an initial marker of raised ICP, and may be an early sign of impending papilloedema.[6] • Papilloedema is swelling (oedema) of the optic nerve head due to raised ICP: • acute stage: oedema at the superior and inferior poles of the disc, absence Multiple abscess Congenital cyst Brain tumour of spontaneous venous pulsation, and enlargement of the blind spot Fig. 5. Selected images of intracranial pathology resulting in raised ICP. • progressive: the whole disc is involved and splinter haemorrhages may be Table 2. evident at the disc margin • chronic stage: gliosis of the optic nerve Eye opening Verbal response Motor response head and eventually optic atrophy with Spontaneous 4 Orientated 5 Obeys commands 6 nerve fibre damage and permanent To verbal command 3 Inappropriate 4 Localises to pain 5 visual field defect. To painful stimulus 2 Incomprehensible 3 Flexion 4 None 1 Makes sounds 2 Abnormal flexion 3 None 1 Extension 2 None 1

Tentorial herniation (lateral) • can follow traction • Third nerve palsy (ptosis, poorly reactive placed on the pituitary stalk and , reduced eye movements) hypothalamus. • False localising (ipsilateral) (Kernohan’s notch) Tonsillar herniation • Depressed level of consciousness from • Neck stiffness as cerebellar tonsils compression compress against the (as • Potentially posterior cerebral artery opposed to meningism from meningitis – occlusion resulting in a homonymous beware of performing a lumbar puncture hemianopia. in the patient with tonsillar herniation) • Elevated blood pressure and slowed Tentorial herniation (central) pulse rate indicate progressive brainstem • Upward gaze palsy results from com- compression pression on the pretectum and superior • Depressed level of consciousness and colliculi will follow persistent • Deteriorating level of consciousness as compression. the blood supply of the and midbrain perforating vessels is Interrogation about vision and examination compromised of the and fundi are extremely

87 CME March 2013 Vol. 31 No. 3 Raised intracranial pressure

• Hutchinson’s pupil is unilateral pupillary objectives of the initial treating physician. dilatation ipsilateral to a supratentorial Table 3. Contraindications to The goals in the acute setting are (usually extrinsic) space-occupying lesion. lumbar puncture[7-9] resuscitation, imaging and neurosurgical This may be the earliest sign of raised ICP • Major contraindication is raised referral. In an unconscious patient, manage and brain shift, but is a sign of imminent intracranial pressure the patient according to Advanced Trauma clinical deterioration. It reflects involvement • Focal neurological deficit Life Support (ATLS) protocols. Intubate of peripheral pupilloconstrictor fibres in • Papilloedema and ventilate the patient to protect their • Significantly altered level of the oculomotor (III) nerve, as a result of consciousness airway if the GCS is 8 or less. An arterial compression on the margin of the tentorium. • Computed tomography (CT) findings blood gas will provide essential information • Kernohan’s notch syndrome raised ICP • lateral midline shift regarding the patient’s oxygenation, as a result of an expanding supratentorial • loss of suprachiasmatic or basal ventilatory and acid-base status. Avoid lesion (e.g. tumour, haematoma) may cisterns hyper- and – it is safest • fourth ventricle effacement cause herniation of brain tissue through to aim for a PaCO of 4 - 4.5kPa. Ensure • obliteration of supracerebellar or 2 the tentorium into the subtentorial quadrigeminal plate cisterns with adequate systemic oxygenation: target an

space, putting pressure on the midbrain. patent ambient cisterns oxygen saturation of at least 95% or a PaO2 If the midbrain is shifted against the • Presence of local infection at lumbar of at least 13 kPa. Maintain normal blood contralateral margin (free edge) of the puncture site pressure – at all times avoid hypotension. • Coagulopathy tentorium, the cerebral peduncle on that • Thrombocytopenia (platelet count Hypoxia and hypotension are potent side may be compressed, resulting in a <50 000) secondary insults that worsen outcome. Be hemiparesis which is ipsilateral to the cautious about treating hypertension as this supratentorial lesion (and hence may be may be a Cushing’s response – the brain may considered ‘false-localising’). There may the aetiology thereof are clear from the be dependent on an elevated BP. Grade the also be palsy ipsilateral imaging. patient’s consciousness after ensuring that to the lesion, which may be partial the patient is haemodynamically stable. A (unilateral pupil dilatation). For trauma, an emergency CT of the detailed neurological exam should follow, The presenting history and clinical situation head is performed as soon as the patient with particular attention paid to pupil size should guide the choice of investigations. is resuscitated. If the presenting history and light reaction, fundoscopy, cranial Invariably patients with a depressed level includes a , a contrast-enhanced nerve palsies, long tract signs, and potential of consciousness will require imaging of CT or MRI will be more useful. If vascular injury in the setting of trauma. the brain. The clinical situation determines pathology is suspected, angiography may also Place the patient with 15 - 30 degrees of head how soon imaging should take place and be indicated. When raised ICP is suspected elevation in a neutral midline position to the choice of imaging. In most cases, but for any reason, it is important not to perform maximise cerebral venous return. Similarly, not all, the diagnosis of raised ICP and a lumbar puncture prior to a CT scan that avoid tight garments and tapings around the would indicate if it is probably safe to do so. neck that cause jugular venous obstruction.

Where meningitis is suspected, a blood culture and septic marker screen (full blood Headache, vomiting and count, C-reactive protein, erythrocyte visual disturbances are sedimentation rate) can be taken and antibiotics started immediately. Do not delay common symptoms of antibiotics until after CSF sampling has been raised ICP. performed. If a subarachnoid haemorrhage is suspected, the presentation of which is not easy to distinguish from spontaneous The goal of primary care management intracerebral haematomas, the first invest- is to stabilise the patient and prevent igation is brain imaging, not a lumbar secondary brain injury by ensuring rapid puncture. If the diagnosis is not clear from transfer to a neurosurgical centre. The use the imaging then a lumbar puncture can be of osmotically active agents (e.g. mannitol) considered. The diagnosis of infectious mass should only be prescribed in consultation lesions (empyema, abscess) requires a search with a neurosurgeon, and only as a for the origin of the lesion. Table 3 lists the temporising intervention until definitive contraindications to lumbar puncture. treatment can be achieved. There is no place for repeated doses in the acute phase. What management should I Mannitol 0.5 g/kg can be given if there is institute? evidence of coning (downward tonsillar Identifying raised ICP and a possible herniation). Hypertonic saline may be a aetiology, along with resuscitation of the better option if this can be used safely. patient where necessary, are the primary After the successful stabilisation and initial

88 CME March 2013 Vol. 31 No. 3 Raised intracranial pressure

treatment, rapid transfer to a centre with and normothermia, while avoiding fever, peak effect is at 40 minutes. Mannitol neurosurgical and intensive care facilities pain, (clinical and subclinical) and will cause an initial plasma expansion is mandatory. When a patient has raised anaemia. that should improve CBF. However, the ICP, similar to , one must recognise BBB becomes permeable to mannitol that ‘time is brain’. and it may worsen vasogenic oedema. When chronic raised ICP is When chronic raised ICP is suspected, early suspected, early imaging Hyperventilation imaging is once again a priority. Further is once again a priority. • Hyperventilation reduces the partial management then depends on the probable pressure of carbon dioxide, which definitive diagnosis. Further management then causes cerebral arteriolar constriction depends on the probable and, therefore, decreased cerebral blood What is likely to happen next? definitive diagnosis. volume, and so ICP. A CT/MRI scan aids in determining the cause • However, hyperventilation also often of the raised ICP – most importantly surgically reduces cerebral blood flow and may correctable causes such as haematomas, Medical interventions worsen or induce ischaemia, and so is intrinsic masses and hydrocephalus that Analgesia, sedation and paralysis inadvisable as a general rule. Still, it may be may warrant emergent surgical intervention. • Agitation and ventilator dysynchrony useful to break a plateau wave of increased Raised ICP due to brain swelling may result in impaired venous return and ICP. Paradoxically, this may increase necessitate monitoring for several days in an aggravation of ICP. oxygenation of the brain because of the ICU setting to guide therapy in trauma and • Adequate analgesia and sedation reduce reduction in ICP. This should be done medical causes of raised ICP. Hydrocephalus agitation, Valsalva and metabolic demand. only in a controlled neurocritical care requires internal or external drainage. Mass • Agents that have the least effect on blood setting. For resuscitation and stabilisation, lesions usually require surgical removal. pressure are preferred to maintain acceptable it is best to aim for a PaCO2 of 4 - 4.5 kPa. ICP can be measured by a number of CPP – short-acting benzodiazepines are Remember to check the arterial blood modalities, commonly: frequently administered. gas; preferably also use end tidal CO2 • an external ventricular drain inserted • Use anticonvulsants if there is a high risk monitoring. into the ventricular system and the of seizures. pressure is transduced • Thiopentone is sometimes used for Hypothermia • an ICP monitor is placed into the refractory ICP: at adequate doses it causes • Hypothermia is not routinely used parenchyma, ventricular or subdural space burst suppression on EEG, reduced to treat raised ICP, although it may and measured with a dedicated unit. metabolic demand and therefore cerebral be considered where raised ICP is blood flow and cerebral blood volume, refractory to other forms of medical Pressure monitoring allows for the inter- and hence ICP. However, thiopentone management. Current evidence from pretation of an absolute value, a temporal commonly reduces blood pressure. clinical trials does not support a clear response and waveforms. The waveforms • Propofol anaesthesia is being utilised in result from systolic blood pressure pulsations adults to reduce the metabolic demand transmitted in the intracranial cavity coupled for oxygen, with the added benefit of with the effects of respiratory cycle on venous improving the seizure threshold. outflow. Lundberg A, B and C waveforms are • Rarely, ICP control necessitates the use identified as pathological.[10] Currently, there of neuromuscular blockade (NMB) are no forms of non-invasive ICP monitoring (prolonged used of NMB is implicated that are accurate enough for clinical use. in the development of myopathies and polyneuropathies). General principles of ICP treatment are to: • maintain ICP less than 20 - 25 mmHg Hyperosmolar therapy • ensure a CPP greater than 60 mmHg • Hypertonic saline (HTS) is increasingly (adults) used rather than mannitol – it remains • avoid and treat factors that may elevate ICP. within the vascular compartment longer than mannitol and so is useful in treating Neurological critical care aims to avoid and the hypovolaemic patient. It also has a treat factors aggravating and precipitating better reflection co-efficient across the intracranial hypertension, and to reduce blood-brain barrier (BBB), i.e. it tends to metabolic requirements. Basic measures cross the BBB less. HTS can also be used to include improving venous return (head treat hyponatraemia, which untreated can positioning), sedation, optimising venti- worsen brain oedema. Ensure that serum lation (avoiding hypoxia, hypo- and sodium is not increased too rapidly. hypercapnia and airway obstruction), • Mannitol lowers the ICP 1 - 5 minutes achieving a euvolaemic state, normotension after intravenous administration, and its

89 CME March 2013 Vol. 31 No. 3 Raised intracranial pressure

benefit of hypothermia in head injury. drainage can be helpful even when the 4. Sankyan N, Vykunta Raju K, Sharma S, Gulati However, for individual patients this ventricles are small, as in trauma. S. Management of raised intracranial pressure. Indian J Paediatr 2010;77:1409-1416. [http:// may be worth trying. The evidence for dx.doi.org/10.1007/s12098-010-0190-2] benefit is stronger for patients who have Decompressive craniectomy 5. Lindsay K. Bone I: and Neurosurgery had a and for neonatal • This is a procedure used occasionally to Illustrated. UK: Churchill Livingstone, 2001. hypoxic ischaemia. treat raised ICP refractory to medical [http://dx.doi.org/10.1136/jnnp.74.1.7] treatment, usually in the context of 6. Jacks AS. Spontaneous retinal venous pulsation: Aetiology and significance. J Neurol Steroids trauma, but also described for cerebral Neurosurg Psychiatry 2003;74:7. [http://dx.doi. • Vasogenic oedema (common with infarction, trauma, subarachnoid and org/10.1136/jnnp.74.1.7] primary and metastatic brain tumours) intracerebral haemorrrhage. 7. Holdgate A. Perils and pitfalls of lumbar puncture responds well to steroid use as a • A large section of the calvarial bone in the emergency department. Emergency Medicine (Fremantle, WA) 2001;13:351. [http:// temporising intervention. Neurological is removed, often with a dural graft to dx.doi.org/10.1046/j.1035-6851.2001.00239.x] deficit secondary to surrounding oedema expand the dura. It increases cranial 8. Linden CH. Cranial computed tomography often responds within 72 hours. However, volume and so reduces ICP. before lumbar puncture. Arch Intern Med the effect diminishes over time. • ICP is consistently reduced with the 2000;160:2868. [http://dx.doi.org/10.1001/ archinte.160.18.2868] • Commonly IV dexamethasone or oral procedure. However, whether this benefits 9. Oliver WJ. Fatal lumbar puncture: Fact versus betamethasone is prescribed. clinical outcome remains controversial. fiction — an approach to a clinical dilemma. • Steroids have no clear role in treating Pediatrics 2003;112:e174. [http://dx.doi. raised ICP secondary to traumatic brain What follow-up should be org/10.1542/peds.112.3.e174] injury or spontaneous haemorrhage. instituted? 10. Citerio G. Intracranial pressure. Intensive Care Med 2004;30:1882. [http://dx.doi.org/10.1007/ Patients with raised ICP are likely to have s00134-004-2377-3] Surgical interventions their long-term care guided by a neurologist Mass lesion removal or a neurosurgeon, depending on the nature • In general, mass lesions causing raised of the underlying pathology. As a general ICP should be removed. physician, one should be vigilant about In a nutshell • Acute lesions must be operated on recognising signs of raised pressure, in • Raised ICP is a common management immediately (haematomas, abscesses, particular in patients with implanted problem in neurosurgical and neurologi- secondary hydrocephalus). devices such as CSF shunts that may be cal services. • Lesions presenting in a subacute or malfunctioning. A close working relationship • Its symptoms, signs and management should be front-of-mind for these treat- chronic fashion require planning for with the specialist, allowing for concerns to ing physicians. optimal management. be discussed timeously, is advantageous. • The clinical manifestations of raised ICP can range from subtle to profound, so CSF drainage References the challenge remains for the generalist to consider the diagnosis, test for proof • External ventricular drain and ventriculo- 1. Dunn LT. Raised intracranial pressure. J Neurol and refer appropriately. peritoneal shunt are quick and reliable Neurosurg Psychiatry 2002;73:i23. • Given that raised ICP is a serious and means of reducing ICP – a small volume 2. Pickard JD. Management of raised intracranial potentially life-threatening emergency, pressure. J Neurol Neurosurg Psychiatry 1993;56:845. fast and reliable referral and transfer of fluid release can significantly lower the [http://dx.doi.org/10.1136/jnnp.56.8.845] mechanisms should be established to IC P. ensure patients with this condition are 3. Rangel CL. Management of intracranial effectively treated. • CSF drainage is of greatest benefit when hypertension. Neurol Clin 2008;26:521. [http:// there is hydrocephalus. Occasionally CSF dx.doi.org/10.1016/j.ncl.2008.02.003]

90 CME March 2013 Vol. 31 No. 3