Neurology

د. حسين محمد جمعه

اختصاصي الامراض الباطنة
البورد العربي
كلية طب الموصل
2011

Stroke: differential diagnosesClinical tips

The common differential diagnoses of a stroke include:
Cardiovascular
Syncope
Subarachnoid haemorrhage
Subdural haematoma
Transient ischaemic attack
Migraine
Carotid artery dissection
Neurological
Todd’s palsy
Cervical myelopathy
Metabolic
Hypoglycaemia or hyperglycaemia
Infectious
Lyme disease
Neoplastic
Cerebral tumour
Unknown cause
Multiple sclerosis
Motor neurone disease
Vestibular neuronitis
Benign paroxysmal positional vertigo
Medically unexplained symptoms


Stroke: differential diagnosesClinical tipsPatients who have had a stroke need urgent brain imaging to exclude a haemorrhage prior to thrombolysis.Blood clots in the middle cerebral artery can be mistaken for subarachnoid blood on a computed tomography (CT) scan.Always check a patient’s blood glucose if they present with acute neurological symptoms.Multiple sclerosis should always be diagnosed by aspecialist.

You see a 33 year old woman in the emergency department who has developed worsening weakness of her right side and has had difficulty finding words over the past few days. She had an episode of vertigo about four years ago, but has no other past medical history and has never smoked. A recent blood test showed that her total cholesterol level was 4.0 mmol/l.

It is unlikely that the patient has had a stroke because the symptoms are of gradual onset over a few days and she has no cardiovascular risk factors.
Symptoms of a stroke usually develop rapidly over seconds or minutes,
whereas symptoms of multiple sclerosis or cerebral tumours tend to take days to weeks. There is no need to start secondary stroke prevention.

The time course of the patient’s symptoms suggests a diagnosis of multiple sclerosis. You should refer the patient to a neurologist so that they can confirm or refute this diagnosis.
The diagnosis of multiple sclerosis is based on finding two or more characteristic neurological events separated in space and time. National guidelines state that only an expert should make a diagnosis of multiple sclerosis.

Learning bite: multiple sclerosis1

You should consider multiple sclerosis in patients younger than 40 years who present with focal neurological symptoms2
According to national guidelines, only a specialist should make the diagnosis of multiple sclerosis
Regarding imaging in patients with possible multiple sclerosis:
MRI is the most sensitive imaging method
Finding lesions in different parts of the central nervous system, occurring at different points in time, supports the diagnosis.

T2 weighted MRI often shows hyperintense lesions in the white matter. These lesions are characteristically ovoid and tend to affect the corpus callosum. Sometimes, they are perpendicular to the margin of the lateral ventricle and then are termed Dawson’s fingers
Hyperintense lesions in the white matter are also seen in scans from people:
With cerebrovascular disease
With Lyme disease
Who are elderly
You may need to perform visual evoked potentials and analysis of the cerebrospinal fluid for oligoclonal .bands to support the diagnosis1


Learning bite: Todd's palsy
This is a combination of neurological signs, such as hemiparesis and dysphasia, that patients may get temporarily following an epileptic seizure. It may mimic a stroke
The cause may be “exhaustion” of the motor cortex following prolonged neuronal activity
The neurological deficit tends to resolve within 48 hours
Sometimes patients have a seizure at the onset of an acute stroke. You may find this situation difficult initially to distinguish from Todd’s palsy. For this reason, when patients have a seizure at the onset of a suspected stroke many experts consider this to be a contraindication to thrombolysis

Thrombolysis is now the established treatment for acute ischaemic stroke.

You should give thrombolysis as soon as possible to maximise the chance of recovery. You should aim for a door-to-needle time of less than one hour
Until recently, only patients presenting within three hours of the onset of symptoms were eligible for thrombolysis. The recent European Cooperative Acute Stroke Study (ECASS) III trial has concluded that this therapeutic window can be extended to four and a half hours.

Alteplase is still licensed for use within three hours following onset. However, this will probably be extended in the near future to four and a half hours. For the time being, you should consider giving thrombolysis off licence three to four and a half hours after the event, on a named patient basis.

Many hospitals have a protocol for giving thrombolysis, based on guidelines from the National Institute for Health and Clinical Excellence (NICE)
Contraindications for thrombolysis include:
• Evidence of intracranial haemorrhage seen on a brain scan
• Rapidly improving symptoms
• Blood pressure greater than 185/110 mm Hg. However, blood pressure may be reduced with labetalol to allow safe thrombolysis
• Seizure at onset of symptoms, due to the difficulty distinguishing acute stroke from Todd’s palsy
• Prior stroke within the last three months
• Warfarin therapy


Learning bite: brain imaging and thrombolysis
All patients considered for thrombolysis need brain imaging to exclude haemorrhage
In the United Kingdom it is common practice to use an unenhanced CT scan of the brain for this
Radiological signs of cerebral infarct are not usually present until several hours after the onset of symptoms.
The purpose of CT, before giving thrombolysis, is to exclude a haemorrhagic cause rather than to show an infarct.

Learning bite: radiological signs of early infarction

Signs seen on a CT or MRI scan within the first few hours of the onset of symptoms may include:
The hyperdense middle cerebral artery sign
An embolus or thrombus within the middle cerebral artery obstructs blood flow, producing a hyperdense or high attenuation signal. Subarachnoid blood can look similar, but it is more generalised, rather than being limited to the area of the middle cerebral artery.

Cerebral oedema around an infarction may appear on CT as:

Effacement of the sulci - cerebral oedema pushes sulci together, making them less visible on a scan.

Learning bite: syncope

When patients present with a loss of consciousness it is important to obtain an account from any witnesses
Loss of consciousness without other neurological symptoms or signs is unlikely to be due to a transient ischaemic attack. You need to consider other conditions such as syncope and epilepsy instead
Aortic stenosis is an important cause of syncope. You can often diagnose this by auscultating the patient’s heart.
If you suspect that a patient has syncope, you need to request a 24 hour ECG. In some patients, you may need to monitor their heart rhythm for longer periods.

Learning bite: migraine

Patients with migraine auras may experience neurological disturbances that are transient. It is sometimes difficult to distinguish migraine from transient ischaemic attacks.
Features of migraine aura without headache include:
Characteristic visual disturbances (for example, flashing lights or fortification spectra)


Symptoms progressing from one body area to another,for example initially paraesthesia and later speech disturbance. This is known as a "march of symptoms” and is typical of migraine aura. Patients with transient ischaemic attacks usually have a sudden onset of neurological symptoms.
Patients with migraine aura are likely to have positive symptoms (such as paraesthesia or visual hallucinations).

In contrast, patients with transient ischaemic attacks are likely to have negative symptoms (such as paresis and visual loss).
Migraine tends to affect a younger age group than transient ischaemic attacks.
On occasion, patients may have a first attack of a migraine aura without headache in their fourth or fifth decade.

You must take care to distinguish central causes of vertigo (such as a cerebellar stroke or brain tumour) from peripheral causes.
You can usually distinguish them by observing the movements of the patient’s eyes. A horizontal nystagmus that does not change with gaze suggests that the vertigo has a peripheral cause.
A patient with a central cause would probably be unable to walk into hospital unaided because of the severity of their symptoms of disequilibrium.

Learning bite: vestibular manoeuvres

The Hallpike manoeuvre
To perform this test, ask the patient to sit upright on a bed or examination couch with their legs extended. Rotate their head by about 45 degrees to one side and extend their neck by about 20 degrees, before lowering them quickly backwards, while supporting their head.

The simplest way to maintain the position of the patient’s head is to have them lie down with their head off the edge of the couch, while you continue to support the weight of their head.
Now observe the patient’s eyes for about a minute.
A positive result for benign positional vertigo is when, after a delay of five to 10 seconds, you see a rotational nystagmus.
The fast phase of the nystagmus is towards the affected ear (the one closest to the ground).

The Epley manoeuvre

This treatment is usually repeated two or three times. Patients can be taught to do it at home. You should warn patients that they may feel dizzy.
Begin by sitting on a bed or couch
Turn your head towards the affected ear and lie on your back.
Remain in this position for five minutes
Turn your head to the other side, and stay in that position for five minutes.
Roll over onto your front, by rolling your body towards the normal ear, and remain on your front for five minutes .Sit up and stay sitting for five minutes


Learning bite: vestibular neuronitis
This condition is due to dysfunction of the peripheral vestibular system
Its cause is unknown, but it often follows an upper respiratory tract infection
The mean age of onset is about 40 years
Clinical features include:
Sudden onset of vertigo, nausea and vomiting, and sweating
A tendency to lean towards the side of the lesion

It is important that you distinguish peripheral from central causes of vertigo:

In peripheral lesions, nystagmus is horizontal and does not change direction with a change in gaze
In central lesions, patients may have:
Nystagmus (vertical or horizontal) that changes direction with a change in gaze
Cranial nerve palsies
Hemiparesis
Dysarthria
Difficulty walking
Medication to control symptoms:
Phenothiazines, such as prochlorperazine
Antihistamines
Benzodiazepines
Steroids


Features of functional hemiparesis may include
A discrepancy between a patient’s reported hemiparesis and their level of activity while on the ward. For example, some patients are able to dress independently in the face of a severe hemiparesis
On examination, limb power tends to initially give way. This is known as “ratchet like weakness.” In hemiparesis due to stroke, the weakness is sustained throughout the range of movement.

You can use Hoover’s test to identify functional hemiparesis.

In Hoover’s test the doctor asks the patient to lie supine and press the heel of their unaffected leg downwards. If the apparently paralysed leg rises slightly, this suggests a non-organic cause for the problem.

Hypoglycaemia may mimic the signs of a stroke. Ideally this should have been checked before requesting the CT scan. You should always check the blood glucose of any patient with acute neurological symptoms, using a bedside stick test.
This patient had an unexplained convulsion and has residual neurological signs. It is probably too early to tell whether the hemiparesis is a Todd’s palsy or whether she had the unusual feature of a convulsion at the onset of a stroke.

Meningitis can cause convulsions, but there is nothing else to suggest the diagnosis. There are more important investigations than lumbar puncture to do at this stage.
A brain tumour can cause convulsions. An unenhanced CT scan may miss small tumours, so an MRI scan (or an enhanced CT scan) might be justified if her blood glucose is normal. But it is preferable to perform simple tests (such as blood glucose) before more complex ones (such as brain scans).