Neurology I Flashcards
(56 cards)
How would you investigate for a brain abscess? [3]
MRI with gadolinium contrast is superior in detecting early cerebritis
CT is useful for detecting complications like hydrocephalus and brain herniation.
Stereotactic needle aspiration can both aid diagnosis and serve as treatment.
NB: Lumbar puncture is contraindicated due to risk of brain herniation.
Describe a key test / feature of early stage frontotemporal dementia? [1]
Constructional apraxia i.e. failure to draw interlocking pentagons may be a key feature in the early stages
What are is the mx of brain abscess? [3]
surgery
* a craniotomy is performed and the abscess cavity debrided
* the abscess may reform because the head is closed following abscess drainage.
IV antibiotics: IV 3rd-generation
* cephalosporin + metronidazole
intracranial pressure management:
* dexamethasone
Describe how you manage NPH [2+]
Shunt Surgery
- Ventriculoperitoneal shunting is the most common surgical intervention, with adjustable valve systems preferred due to their ability to regulate cerebrospinal fluid flow based on individual patient needs.
- First-line treatment in the acute setting is usually insertion of an external ventricular drain
- Regular monitoring post-surgery is important to detect complications such as infection, overdrainage, underdrainage, and mechanical shunt failure.
Non-Surgical Management
* While shunting is the primary treatment modality, non-surgical options may include lifestyle modifications such as avoiding medications that can exacerbate symptoms (e.g., sedatives, anticholinergics).
* Physiotherapy may be beneficial in managing gait disturbances.
How does a patient with Lambert-Eaton syndrome present? [5]
Weakness in muscles of the proximal arms and legs
Weakness effects legs more than arms (causes difficulty climbing stairs / rising from seat)
Weakness is noramlly relieved temporarily after start of exercise
Autonomic dysfunction, causing dry mouth, blurred vision, impotence and dizziness
Reduced or absent tendon reflexes
NB:
- ophthalmoplegia and ptosis not commonly a feature (unlike in myasthenia gravis)
Explain how you treat Lambert-Eaton syndrome [4]
treatment of underlying cancer
immunosuppression, for example with prednisolone and/or azathioprine
Amifampridine works by blocking voltage-gated potassium channels in the presynaptic membrane, which in turn prolongs the depolarisation of the cell membrane and assists calcium channels in carrying out their action.
intravenous immunoglobulin therapy and plasma exchange may be beneficial
Describe the classic clinical presentation of mysanthenia gravis [+]
The critical feature is weakness that worsens with muscle use and improves with rest. Symptoms are typically best in the morning and worst at the end of the day.
The symptoms most affect the proximal muscles of the limbs and small muscles of the head and neck, with:
- Difficulty climbing stairs, standing from a seat or raising their hands above their head
- Extraocular muscle weakness, causing double vision (diplopia)
- Eyelid weakness, causing drooping of the eyelids (ptosis)
- Weakness in facial movements
- Difficulty with swallowing
- Fatigue in the jaw when chewing
- Slurred speech
- generalized weakness, including respiratory muscle involvement, which can be life-threatening (myasthenic crisis).
What investigations do you conduct for MG [4]
Ztf:
.1. Antibody testing:
- AChR antibodies (around 85%)
- MuSK antibodies (less than 10%)
- LRP4 antibodies (less than 5%)
.2. A CT or MRI of the thymus gland is used to look for a thymoma.
.3. Edrophonium test:
- Patients are given intravenous edrophonium chloride
- Normally, cholinesterase enzymes in the neuromuscular junction break down acetylcholine. Edrophonium blocks these enzymes, reducing the breakdown of acetylcholine
- As a result, the level of acetylcholine at the neuromuscular junction rises, temporarily relieving the weakness.
- A positive result suggests a diagnosis of myasthenia gravis.
PM:
Repetitive nerve stimulation (RNS):
- repetitive electrical stimulation of a peripheral nerve while recording the compound muscle action potentials (CMAPs) from a target muscle.
- A decline in the amplitude of CMAPs after repetitive nerve stimulation, known as decrement, supports the diagnosis of MG.
Single-fiber electromyography (SFEMG):
- This is the most sensitive test for MG, which measures the variability in the time it takes for individual muscle fibres to respond to nerve stimulation (jitter) and the failure of some fibres to respond at all (blocking).
- Abnormal jitter and blocking are indicative of impaired neuromuscular transmission in MG.
NB:
- due to the potential side effects and limited specificity, edrophonium test has been largely replaced by more specific and sensitive diagnostic tests.
Describe 4 treatment options for MG [4]
Pyridostigmine is a cholinesterase inhibitor that prolongs the action of acetylcholine and improves symptoms. First-line
Immunosuppression (e.g., prednisolone or azathioprine) suppresses the production of antibodies
Thymectomy can improve symptoms, even in patients without a thymoma
Rituximab (a monoclonal antibody against B cells) is considered where other treatments fail
Intravenous immunoglobulin (IVIg) or plasma exchange may be considered in severe cases or during myasthenic crisis.
How do you investigate for LES? [1]
EMG
- incremental response to repetitive electrical stimulation
How do you differentiate LES vs MG? [3]
Clinically, LES typically presents with proximal muscle weakness that improves with repeated use (unlike MG where symptoms worsen with use).
Autonomic symptoms such as dry mouth or impotence are common in LES but rare in MG.
Ophthalmoplegia and bulbar symptoms are less common in LES compared to MG.
Management of Myasthenic Crisis? [2]
In a myasthenic crisis, immediate hospitalisation is required.
Intensive respiratory support may be necessary, including intubation and mechanical ventilation if there is impending respiratory failure.
Rapid short-term symptom control can be achieved by plasma exchange or IVIg.
Describe possible risks of overmedication w treating MG? [1]
Cholinergic Crisis:
- Overmedication with anticholinesterase drugs can cause muscle fasciculations, increased salivation, diarrhoea, and bradycardia. Differentiation from myasthenic crisis is critical for appropriate management.
Lecture:
Describe the EMG seen in MG c.f. non-MG person [2]
A normal NMJ has enough reserve to generate normal CMAP (compound muscle action potential)
A myasthenic NMJ doesn’t have enough reserve to generate normal CMAPs (decrement >10%) due to blocking antibodies at post-synaptic Acetylcholine receptors.
Lecture
Describe how someone in MG crisis would present in an assessment ?
Assessment:
- Tiring in conversation,
- Increased RR
- accessory muscles
- unable to lie flat (FVC reduces 20% on lying down)
- ** weak neck flexion** (same spinal levels as phrenic nerve C2-4).
In MG Resp. crisis - what investigation would you do and how would this inform your mx plan? [2]
Assessment: BEDSIDE SPIROMETRY - FVC (not peak flow/FEV1):
- >20ml/kg (1.5-2.0L) – on repeated measures – ABG and Rapid response/anaesthetic review – consideration of HDU/ITU
- >15ml/kg (1L) – urgent Rapid response/anaesthetic review and ITU transfer
Most commonly first-line medication for focal seizures - lamotrigine or levetiracetam
Increased appetite and weight gain, alopecia, P450 enzyme inhibitor
P450 enzyme inducer, dizziness and ataxia, drowsiness, agranulocytosis, SIADH
Is most associated with which drug? [1]
carbamazepine
P450 enzyme inducer, dizziness and ataxia, drowsiness, gingival hyperplasia, coarsening of facial features
What is the first-line treatment of myoclonic seizures? [1]
Sodium Valproate
First line antiepileptic for generalised seizures in young women? [1]
Lamotrigine (or levateracetam)
With Horners, anhydrosis determines the site of the lesion. The causes can be remembered as the 4 Ss, 4 Ts and 4 Cs.
Describe the causes of these lesions [+]
Central lesions (4 Ss):
* S – Stroke
* S – Multiple Sclerosis
* S – Swelling (tumours)
* S – Syringomyelia (cyst in the spinal cord)
Pre-ganglionic lesions (4 Ts):
* T – Tumour (Pancoast’s tumour)
* T – Trauma
* T – Thyroidectomy
* T – Top rib (a cervical rib growing above the first rib above the clavicle)
Post-ganglionic lesion (4 Cs):
* C – Carotid aneurysm
* C – Carotid artery dissection
* C – Cavernous sinus thrombosis
* C – Cluster headache
Painful Horners = source? [1]
Painful Horners = Carotid dissection
