17 Neurological disease
Approach to the patient
Imaging plays a key role in diagnosis.
• CT is the investigation of choice in an acutely ill patient, particularly if intubated. It is quick and readily available. Acute haemorrhage is easily visualized. CT resolution is increased by using thinner slices but disadvantages include its failure to detect lesions whose attenuation is similar to that of the brain (e.g. subdurals and strokes during the isodense phase) or to that of the bone if the lesion is near the skull vault. Posterior fossa structures are poorly resolved. On modern scanners CT angiography is now the non-invasive neurovascular imaging modality of choice.
• MRI has great advantages over CT, with superior soft-tissue differentiation making it the best imaging modality to delineate brain parenchyma and spinal cord anatomy and pathology. Tumours, infarction, multiple sclerosis plaques and lesions of the cord and nerve roots are well demonstrated. Intracerebral and extracranial (carotid) blood vessels can be imaged without contrast. Diffusion-weighted imaging is sensitive for early infarction in stroke and allows differentiation between recent and old ischaemic lesions. Other advantages of MRI include multi-planar imaging in axial, sagittal and coronal planes, and absence of ionizing radiation. Disadvantages include longer imaging times than CT scanning, claustrophobia for some patients, inability to image patients with pacemakers and difficulty monitoring severely ill or ventilated patients while in the scanner.
Alterations in consciousness
• Coma is a state of unrousable unresponsiveness (often defined as a Glasgow Coma Score (GCS) of 8 or less; Table 17.1). GCS is a useful and reliable standardized tool, especially for serial measurements, but be aware of limitations, e.g. tetraparetic patients or those with tracheostomy.
• State of arousal is influenced by the central reticular activating system (extends from brainstem to thalamus) and its interactions with cortex, hypothalamus, cerebellum and sensory stimuli. Consequently, coma results from two main processes:
• diffuse metabolic/toxic/neurological dysfunction or other disorders affecting extensive areas of cortex (e.g. drugs, toxins or hypoxia)
Table 17.1 Glasgow Coma Score (GCS)
| Category | Response | Score |
|---|---|---|
| Eye opening (E) | Spontaneous | 4 |
| To speech | 3 | |
| To pain | 2 | |
| Nil | 1 | |
| Speech/verbal response (V) | Appropriate and orientated | 5 |
| Confused | 4 | |
| Inappropriate words | 3 | |
| Incomprehensible sounds | 2 | |
| Nil | 1 | |
| Motor response (M) | Obeys commands appropriately | 6 |
| Localizes to pain | 5 | |
| Withdraws to pain | 4 | |
| Flexes to pain | 3 | |
| Extends to pain | 2 | |
| Nil | 1 |
GCS = E + V + M. Minimum score 3, maximum score 15.
Coma is a life-threatening emergency. Assessment must be swift and comprehensive, and occur in tandem with life support measures and initial investigations (Box 17.1, p. 624, and see Fig. 20.21 (p. 722)).
Box 17.1 Management of the comatose patient
This is a neurological emergency (see also Fig. 20.21). Enlist the help of an experienced nurse. The immediate priority is cardiorespiratory resuscitation.
• Check pulse/BP and breathing. Resuscitate if necessary. Place on continuous cardiac and oximetry monitoring
• Secure IV access and give 50 mL of 50% glucose. In patients with suspected alcohol use, the glucose should be preceded by 250 mg thiamine IV (to prevent Wernicke’s encephalopathy)
• Treat seizures (lorazepam and phenytoin — see Box 17.4) and suspected bacterial meningitis (p. 54)
Initial assessment
• Assess vital signs and airway safety. Guedel airway insertion may be necessary. Is intubation/ventilation or circulatory support required?
• General examination. Look for clues to the cause of coma. Is there fever, purpuric rash, shock, anaemia, liver disease, melaena or renal disease, e.g. haemodialysis shunt or injection marks? Is there a MedicAlert bracelet? Is there evidence of trauma — blood or CSF in ears/nose or bruising (battle sign or ‘racoon eyes’ indicating skull fracture)? Neck stiffness can still be detected in unconscious patients and is indicative of meningeal infection or subarachnoid haemorrhage (SAH).
• Neurological examination. This is helpful to lateralize signs, to determine the level of pathology and to assess integrity of brainstem reflexes.
• Pupil size and reaction to light. These are of great diagnostic significance in coma. Unilateral fixed dilated pupil indicates 3rd nerve compression or stretch, and suggests herniation of the uncus of the temporal lobe through the tentorial hiatus (coning) or posterior communicating artery aneurysm. Bilateral fixed and dilated pupils follow as coning progresses and indicate imminent death, but can also occur in deep coma of any cause, e.g. tricyclic overdose and hypothermia. Bilateral pinpoint pupils occur in opiate overdose and pontine lesions. Small reactive pupils are usually found in toxic and metabolic coma.
• Eye position and movements. Conjugate deviation of eyes may indicate a frontal hemispheric lesion, e.g. stroke (eyes deviated towards lesion, away from hemiplegic side) or pontine lesion (eyes away from lesion). Disconjugate eye position may indicate a brainstem lesion. Roving eye movements (‘windscreen wiper eyes’) are seen in light metabolic coma or diffuse cortical injury.
• Other brainstem reflexes. Look for the corneal reflex, gag reflex (or cough reflex with suction catheter via endotracheal tube), (if spine is stable) doll’s eye movements, and assess pattern and effort of respiration.
Investigations where cause of coma is unknown after initial assessment
• CT brain is the priority once the patient is stabilized and glucose checked, especially if lateralizing neurological signs are present, e.g. hemiparesis. Note that raised intracranial pressure (ICP) cannot always be excluded with imaging; specialist review of imaging may be required to look for features of raised pressure such as early cerebral oedema or effacement of chiasmatic cisterns.
• Lumbar puncture (LP) and CSF examination should be performed only after risk assessment and if there is no CT evidence of a mass lesion or raised ICP.
N.B. Treat suspected bacterial meningitis with IV antibiotics and high-dose steroids immediately — BEFORE lumbar puncture.• Lumbar puncture is contraindicated in meningococcal septicaemia (p. 54). If viral encephalitis is a possibility (p. 55), start IV aciclovir 10 mg/kg 3 times daily (monitor renal function).
Acute confusional state (delirium)
Delirium is characterized by abnormalities of perception and cognition, often without a decrease in the level of consciousness. Impairment in consciousness, if present, can vary and fluctuates with confusion, usually being worse at night. It is very common, especially in elderly hospitalized patients. There are a wide variety of causes, often occurring in combination, in a patient vulnerable by virtue of age or impaired cognitive reserve. Common causes include systemic infection, hypoxia, electrolyte imbalance, liver or renal failure, and drug/alcohol intoxication or withdrawal (especially anticonvulsants, anxiolytics, opiates), as well as brain injury, encephalitis/meningitis or deficiency states such as Wernicke–Korsakoff encephalopathy.
Management
• Initial management and evaluation is similar to that of the comatose patient. Review the notes, take a history and examine the patient.
• General measures include nursing in moderately lit, quiet room, repeated reassurance, and correction of metabolic imbalance. Perform appropriate investigations to determine the cause and treat underlying disease. Sedation must be used judiciously, as occasionally paradoxical worsening of confusion can result, particularly with benzodiazepines. Give haloperidol 1 mg oral twice daily if patient presents risk to themselves or others.
Delirium tremens (DTs)
This is the most serious alcohol withdrawal state and occurs 1–3 days after alcohol cessation. Patients have disorientation, agitation, tremor and visual hallucinations. For treatment, see Box 17.2.
Stroke
N.B. Stroke is a medical emergency and prompt treatment can improve prognosis.
Pathophysiology
• Ischaemic stroke (infarction of central nervous tissue) results from cerebral infarction secondary to either arterial thromboembolism or emboli arising from the heart (e.g. in atrial fibrillation, mural thrombus after acute myocardial infarction, or rarely from vegetations in infective endocarditis).
• Cerebral haemorrhage accounts for ~15% of strokes and is often caused by microaneurysm rupture in small penetrating arteries in hypertensive patients; occasionally by aneurysm or arteriovenous malformation rupture; or by amyloid angiopathy in older patients.
Clinical evaluation
• General physical examination
• Check for fever to exclude a possible infective aetiology; look for altered mental state (possible meningo-encephalitis).
• Look for systemic signs of underlying disease, e.g. evidence of vasculitis, stigmata of infective endocarditis.
• Cardiovascular examination should include pulse (atrial fibrillation?), BP, carotids for bruits and heart for murmurs.
• Neurological examination localizes the lesion to anterior or posterior circulation territory.
• Anterior circulation. Middle cerebral artery (MCA) or anterior cerebral artery (ACA) and branches (carotid artery distribution). Hemispheric infarction typically causes a combination of contralateral limb/facial weakness and/or sensory loss, visual field defects, dysphasia/aphasia or sensory inattention (especially in right hemisphere stroke). Initially the affected limbs are flaccid (hypotonia), but this progresses to spasticity with upper motor neurone (UMN) signs.
• Posterior circulation. Vertebral, basilar and posterior cerebral arteries and branches. Brainstem infarction may result in a combination of ataxia, long tract signs and cranial nerve palsies. The lateral medullary syndrome causes a characteristic clinical picture, which includes ipsilateral facial numbness, diplopia, nystagmus and ataxia. Posterior cerebral artery (PCA) infarction results in visual field defects. Posterior circulation stroke may lead to coma.
Stroke is primarily a clinical diagnosis, supported by imaging.
Immediate management (see Emergencies in Medicine p. 721)
• Resuscitate the patient, including administration of oxygen; establish IV access, oximetry and cardiac monitoring. Decide whether thrombolysis is appropriate.
• Take blood for FBC, ESR (raised in giant cell arteritis (GCA), infective endocarditis), U&E, creatinine and glucose; if appropriate, test for sickle cell disease.
• Imaging in acute stroke
• Non-contrast CT will demonstrate haemorrhage immediately but cerebral infarction is often not detected or only subtle changes are seen acutely (Fig. 17.1A).
• Diffusion-weighted MRI (DWI) shows changes early in infarction (Fig. 17.1B) and may distinguish between acute and chronic areas of ischaemia. It is more sensitive than CT for small infarcts and for the detection of haemorrhage. If MRI is unavailable a CT should be performed so that there is no delay in giving thrombolysis.
Thrombolysis (Box 17.3)
N.B. Every minute counts. The benefit of thrombolysis decreases with time, even within the 4.5-hour window.• Exclude patients with strokes due to haemorrhage, infection or other non-ischaemic pathologies (Box 17.3).
Box 17.3
(Amended from Adams HP, et al. 2007)
Thrombolysis in acute ischaemic stroke
Exclusion criteria
Clinical
• Persistent systolic BP ≥ 185 mmHg, diastolic BP ≥ 110 mmHg, or requiring aggressive therapy to control BP
Further management
• Admit to a stroke unit. Specialist care, including nursing, physiotherapy, speech and language therapy and occupational therapy, on a dedicated stroke unit improves outcome. Maintain hydration, perform swallowing assessment for aspiration risk, and turn regularly to avoid pressure sores. Try to avoid catheterization if possible. Do not lower BP in the acute phase unless hypertensive encephalopathy or other acute complications of severe hypertension (e.g. hypertensive nephropathy, hypertensive cardiac failure/acute myocardial infarction, aortic dissection, eclampsia) are present. Hyperglycaemia is associated with poorer outcome, so maintain normoglycaemia with insulin if required. Treat infections.
• Secondary prevention
• Do not give antiplatelet drugs within 24 hours of recombinant tissue-type plasminogen activator (rt-PA). Then start clopidogrel 75 mg per day. Treatment with modified release dipyridamole (200 mg × 2 daily) in combination with aspirin (300 mg/day loading dose, then 75–150 mg/day) is now recommended only if clopidogrel is contraindicated or not tolerated (see NICE guidelines 2010).
• Modify risk factors, particularly hypertension, hypercholesterolaemia, diabetes and smoking. Sustained hypertension persisting beyond 2 weeks should be treated (target BP < 140/85 mmHg or 130/80 mmHg if diabetic). All patients should be on a statin (e.g. simvastatin 40 mg) unless cholesterol < 3.5, started 48 hours after stroke.
• Identification of embolic source
• Carotids. All patients with anterior circulation stroke who are not severely disabled by the stroke should have carotid imaging with Doppler or MRI/CT angiography to identify symptomatic carotid stenosis. Early carotid endarterectomy greatly reduces the risk of further stroke if there is 70–99% stenosis on the affected side. Benefits for 50–69% stenosis and for asymptomatic > 70% stenosis are more modest.
• Cardiac source. Perform echocardiography to identify a cardiac source of embolism if an embolic stroke is possible. Transoesophageal echocardiography (TOE) is appropriate in younger patients with cryptogenic stroke, e.g. to identify a patent foramen ovale (PFO) or if endocarditis is suspected. Twenty-four-hour ECG monitoring is used to identify paroxysmal atrial fibrillation. Anticoagulation should be initiated in atrial fibrillation or if cardiac thrombus is present — generally wait 2 weeks after the acute event before starting anticoagulation to reduce the risk of haemorrhagic transformation, unless dealing with a lacunar or small stroke.
• Treat or prevent complications. DVT prophylaxis with SC low molecular weight heparin (LMWH), e.g. enoxaparin 40 mg SC daily (N.B. not in haemorrhagic stroke). Treat complications early, e.g. depression, seizures, pneumonia. If patient deteriorates neurologically, repeat brain imaging. Intracerebral haematoma, for example, might require urgent neurosurgical intervention.
Transient ischaemic attacks (TIAs)
• Examination for cause: look for atrial fibrillation, hypertension, carotid artery bruit and valvular heart disease.
• TIAs may herald the onset of stroke (one-quarter of patients developing stroke have had a TIA, usually within the previous week).
• The ABCD2 score can help to stratify stroke risk in the first 2 days.
| •Age > 60 years | 1 point |
| •BP > 140 mmHg systolic and/or > 90 mmHg diastolic | 1 point |
| •Clinical features | |
| Unilateral weakness | 2 points |
| Isolated speech disturbance | 1 point |
| Other | 0 points |
| •Duration of symptoms (mins) | |
| > 60 | 2 points |
| 10–59 | 1 point |
| < 10 | 0 points |
| •Diabetes | |
| Present | 1 point |
| Absent | 0 points |
• If patients are considered to have had a high-risk TIA, i.e. ABCD2 score > 4, or have had two recent TIAs, especially within the same vascular territory, then they should be admitted for investigation and commencement of secondary prevention.
• All patients should be referred to a TIA clinic and ideally seen within 24 hours. Investigation and treatment should be regarded as urgent and should be completed within 2 weeks.
