Neurology 3 Flashcards
What is Mysthenia Gravis?
Myasthenia gravis is an autoimmune disorder resulting in insufficient functioning acetylcholine receptors.
Key features of myasthenia gravis
The key feature is muscle fatigability - muscles become progressively weaker during periods of activity and slowly improve after periods of rest:
extraocular muscle weakness: diplopia
proximal muscle weakness: face, neck, limb girdle
ptosis
dysphagia
what is associated with myasthenia gravis?
thymomas in 15%
autoimmune disorders: pernicious anaemia, autoimmune thyroid disorders, rheumatoid, SLE
thymic hyperplasia in 50-70%
Investigations for Myasthenia gravis?
single fibre electromyography: high sensitivity (92-100%)
CT thorax to exclude thymoma
CK normal
antibodies to acetylcholine receptors
positive in around 85-90% of patients
n the remaining patients, about about 40% are positive for anti-muscle-specific tyrosine kinase antibodies
Tensilon test: IV edrophonium reduces muscle weakness temporarily - not commonly used any more due to the risk of cardiac arrhythmia
Management of myasthenic crisis
plasmapheresis
intravenous immunoglobulins
What does the fourth cranial nerve supply?
The fourth cranial nerve (trochlear nerve) supplies the superior oblique muscle
this muscle is crucial for rotating the eye downward and outward
by innervating the superior oblique muscle, the trochlear nerve enables the eye to look down when it is adducted (moved towards the nose). This movement is particularly important for actions like going downstairs or reading.
What are the features of a 4th nerve palsy?
vertical diplopia
classically noticed when reading a book or going downstairs
subjective tilting of objects (torsional diplopia)
the patient may develop a head tilt, which they may or may not be aware of
when looking straight ahead, the affected eye appears to deviate upwards and is rotated outwards
How does an abducens nerve palsy present?
Abducens nerve palsy typically presents with horizontal diplopia owing to weakness in the lateral rectus muscle, which impairs abduction of the affected eye. Patients usually exhibit an esotropia (inward deviation of the affected eye) that becomes more pronounced when gazing towards the lesioned side.
How does an oculomotor never palsy present?
Oculomotor nerve palsy generally results in ptosis and impaired adduction, elevation and depression of the affected eye, leading to a ‘down-and-out’ resting position. Pupillary involvement may suggest a compressive etiology such as an aneurysm.
What does superior oblique myokymia cause?
it causes episodic monocular vertical oscillations rather than constant vertical diplopia. Patients often report sensations akin to ‘quivering’ within their eye
what is MS?
Multiple sclerosis is chronic cell-mediated autoimmune disorder characterised by demyelination in the central nervous system.
What are the different subtypes of MS?
Relapsing-remitting disease
most common form, accounts for around 85% of patients
acute attacks (e.g. last 1-2 months) followed by periods of remission
Secondary progressive disease
describes relapsing-remitting patients who have deteriorated and have developed neurological signs and symptoms between relapses
around 65% of patients with relapsing-remitting disease go on to develop secondary progressive disease within 15 years of diagnosis
gait and bladder disorders are generally seen
Primary progressive disease
accounts for 10% of patients
progressive deterioration from onset
more common in older people
Patient with MS on Natalizumab and becomes confused - what may be causing new onset confusion?
Progressive multifocal leukoencephalopathy (PML) is associated with natalizumab treatment in multiple sclerosis (MS). It is caused by reactivation of the JC virus due to immunodeficiency secondary to natalizumab (it can also occur with a few other MS modifying drug treatments and HIV). The reactivation of the JC virus causes demyelination and the symptoms a patient has depends on the site and extent of the demyelination. The most common symptoms are confusion, behavioural change, ataxia, hemiparesis and visual deficits.
when may anti-epileptics be started after firs seizure?
the patient has a neurological deficit
brain imaging shows a structural abnormality
the EEG shows unequivocal epileptic activity
the patient or their family or carers consider the risk of having a further seizure unacceptable4
Management of generalised tonic clonic seizures?
males: sodium valproate
females: lamotrigine or levetiracetam
girls aged under 10 years and who are unlikely to need treatment when they are old enough to have children or women who are unable to have children may be offered sodium valproate first-line
Management of focal seizures?
first line: lamotrigine or levetiracetam
second line: carbamazepine, oxcarbazepine or zonisamide
Management of abscence siezures?
first line: ethosuximide
second line:
male: sodium valproate
female: lamotrigine or levetiracetam
carbamazepine may exacerbate absence seizures
Management of myoclonic seizures?
males: sodium valproate
females: levetiracetam
Mangement of tonic or atonic seizures?
males: sodium valproate
females: lamotrigine
what may cause an upbeat nystagmus?
cerebellar vermis lesions
What may cause a down beart nystamus?
Arnold-Chiari malformation
why does raised ICP cause third nerve palsy?
Increased pressure within the cranium secondary to the rapid expansion of intracranial haematoma can cause the temporal lobe to herniate through the tentorial notch. This herniation can compress the ipsilateral third cranial nerve, resulting in a dilated pupil, ptosis and ‘down and out’ eye deviation.
what does the facial nerve supply?
The facial nerve is the main nerve supplying the structures of the second embryonic branchial arch. It is predominantly an efferent nerve to the muscles of facial expression, digastric muscle and also to many glandular structures. It contains a few afferent fibres which originate in the cells of its genicular ganglion and are concerned with taste.
Supply - ‘face, ear, taste, tear’
face: muscles of facial expression
ear: nerve to stapedius
taste: supplies anterior two-thirds of tongue
tear: parasympathetic fibres to lacrimal glands, also salivary glands
causes of bilateral facial nerve palsy?
Causes of bilateral facial nerve palsy
sarcoidosis
Guillain-Barre syndrome
Lyme disease
bilateral acoustic neuromas (as in neurofibromatosis type 2)
as Bell’s palsy is relatively common it accounts for up to 25% of cases f bilateral palsy, but this represents only 1% of total Bell’s palsy cases