Limb Weakness Flashcards
What does time course tell you about the possible cause of limb weakness
Sudden (within minutes): trauma (displaced vertebral fractures due to major trauma) or vascular insults (stroke, TIA)
Subacute (hours-days): progressive demyelination (GBS, MS) or slowly expanding haematoma (subdural)
Chronic (weeks to months): slow growing tumour or MND
What is the neuronal pathway for muscles
Cerebral cortex Corona radiata Internal capsule Pons Corticospinal tract + spinal cord Nerve root Peripheral nerve NMJ Muscle
What are the differentials for sudden onset limb weakness
Ischaemic Stroke Transient ischaemic attack (TIA) Haemorrhagic stroke Hemiplegic migraine, Todd's palsy, hypoglycaemia Spinal disc prolapse Spinal cord transection or infarction Vertebral fracture Acute limb ischaemia Traumatic nerve injury
What are the differentials for subacute onset limb weakness
Multiple Sclerosis Haematoma (subdural, extradural) Tumour Abscess Guillain-Barré syndrome Transverse myelitis Poliomyelitis Botulism Tetanus
What are the differentials for chronic onset limb weakness
Spinal canal stenosis Vitamin B12 deficiency Diabetes mellitus Vasculitis Myasthenia gravis Lamber-Eaton syndrome Myositis
What questions should be asked about limb weakness on presentation
Exact time of onset (stroke management)
Any speech disturbance or visual disturbance (suggests brain rather than peripheral pathology)
Headache? (SAH, hemiplegic migraine, intracranial mass)
Seizure or LOC? (Todd’s paresis)
Neck or back pain? (disc prolapse, traumatic injury to spine, discitis, spinal abscess)
Trauma? (slow expanding subdural haematoma)
Risk factors for stroke? (HTN, DM, hypercholesterol, FMHx, smoking)
What are the signs of UMN and LMN lesions
UMN: Hypertonia Hyperreflexia Upgoing plantars (Babinski's) Clonus
LMN: Hypotonia Hyporeflexia Fasciculations Wasting and muscle atrophy
What do language defects in the presence of the limb weakness suggest about pathology
Pathology in the cortex of the dominant hemisphere (usually left)
Receptive dysphasia: patient speaks fluently but cannot comprehend language. Lesion in Wernicke’s area in the temporal lobe
Expressive dysphasia: patient can comprehend and follow instructions but cannot find words or speak fluently. Lesion in the Broca’s area in the frontal lobe
What do attention defects in the presence of limb weakness suggest
Parietal cortex lesion
Patient ignores half of the sensory world i.e. responding to cues only one side
What do eye signs in the presence of limb weakness suggest
Complete blindness: optic nerve (e.g. optic neuritis) or the globe
Homonymous hemianopia: lesion between the optic chiasm and visual cortex on the contralateral side
Eye deviation: eyes deviating away from the weak side - cortical lesion. Towards the weak side - brainstem lesion
What investigations should be ordered for suspected stroke
Urgent CT head (non-contrast)
FBC: may reveal cause for arterial occlusion (polycythaemia, thrombocytosis) or haemorrhage (thrombocytopenia)
Glucose: exclude hypoglycaemia
Clotting studies: exclude haemophilia or coagulopathy
ECG: look for AF (May cause emboli)
What is the acute management for ischaemic stroke
Antiplatelets (typically aspirin) as soon as haemorrhagic stroke has been excluded, but delayed 24h if the patient receives thrombolysis
VTE prophylaxis using LMWH or pneumatic compression devices to the calves
Transfer to stroke unit/specialist ward for specialist nursers, SALT, physiotherapists and social workers
What second line investigations should be done to patients after transfer to the stroke unit
Carotid doppler ultransonography: USS of the carotid arteries will identify or exclude carotid artery atheromas that may be the cause of emboli causing the stroke
Echo cardiogram: identify a cardiac source of emboli e.g. atrial thrombus from AF, recent MI, heart murmur | patents foramen ovale
What complications of stroke should you be worried about and what can you do to minimise the likelihood of them occurring
Pressure ulcers -> regularly move the patient or placing on an inflatable mattress that periodically varies the area of pressure
Aspiration pneumonia -> SALT carries out a swallowing assessment, consider a NG tube
VTE and recurrent ischaemic stroke: LMWH and pneumatic compression devices to the calves
What forms the disability screen for patients with suspected stroke
GCS (uses the best side) Swallow Speech and language Visual fields Gait
What does a carotid bruit suggest and how is the cause treated
Carotid artery stenosis due to atherosclerotic disease
Causes an embolus -> stroke
Have a duplex USS of the carotid arteries
Stenosis >70% - carotid endarterectomy
What is the follow up management for patients who have had an ischaemic stroke
Stop smoking
Daily antiplatelets (clopidogrel)
Statins, even if cholesterol levels are normal
Daily ACEi and/or thiazide diuretic
GP should follow up on any risk factors
What is the management for TIA
Establish the source of emboli and treat it
300mg daily aspirin
Referral to a specialist TIA clinic (urgency depends on ABCD2 score, which predicts risk of stroke in the 48h after a TIA)
What screening is done at a TIA clinic
Smoking
Hypertension
Hyperlipidaemia: fasting lipid profile
Diabetes mellitus: random plasma glucose, fasting glucose, HbA1c
Carotid artery stenosis: Doppler i;trasound of the carotid arteries
Atrial fibrillation: ECG
62M who has recent onset of leg weakness. Noticed the legs becoming weak a fortnight ago and he was unable to get out his chair. It progressed so that he had to use a walking frame and for the past 2 days he has not been able to walk.
Exam - increased tone and clonus
Reduced power (2/5 bilaterally on hip and knee flexion)
Brisk patellar and ankle reflexes
Upgoing plantars
Loss of vibration sensation before the hips and pinprick below the umbilicus
Anal sphincter tone and perianal sensation are normal and all other systems including upper limbs are normal
What is the diagnosis and what investigation should be ordered
UMN lesion + loss of sensation below the umbilicus (T10 dermatome)
Most likely cord compression (disc herniation, spondylolisthesis, SOL e.g. tumour, abscess, cyst, haematoma)
Order a spinal MRI
What investigations should be ordered for Multiple Sclerosis
Lumbar puncture: Elevated IgG antibodies in the CSF - oligoclonal bands that is unmatched with the serum
MRI brain and spinal cord: looking for plaques
Visually evoke potentials: Delayed response to visual stimulation indicates slow electrical conduction and a lesion along the optic pathway
What are the contraindications to thrombolysis for stroke
Onset cannot be confirmed as within 4.5 hours
Acute intracranial haemorrhage on CT
Seizure at onset of stroke
Symptoms suggest SAH
Stroke or serious head injury in the preceding 3 months
Major surgery or serious trauma within 2 week s
Previous intracranial haemorrhage
Intracranial neoplasm
Arteriovenous malformation or aneurysm
etc.
What scale is used to grade limb weakness
MRC scale for power
0/5: No movement
1/5: flicker is perceptible in the muscle
2/5: Movement only if gravity is eliminated
3/5: can move the limb against gravity
4/5: Can move the limb against gravity and some resistance exerted by the examiner
5/5: normal power
Where is the neurological lesion likely to be for hemiparesis
Weakness on one half of the body
Contralateral cerebral motor cortex (widespread stroke)
Contralateral corona radiata, internal cortex, pons e.g. stroke
Where is the neurological lesion likely to be for limb hemiparesis
Weakness unilaterally in the limbs
Contralateral cerebral motor cortex e.g. stroke
Contralateral corona radiata, internal cortex, pons e.g. stroke
Ipsilateral spinal lateral motor tract e.g. cervical disc prolapse
Where is the neurological lesion likely to be for isolated limb weakness
Contralateral cerebral motor cortex e.g. localised stroke
Contralateral corona radiata, internal cortex, pons e.g. stroke
Ipsilateral peripheral nerve root e.g. osteophyte
Ipsilateral peripheral nerve plexus e.g. trauma to brachial plexus
Ipsilateral peripheral nerve per se e.g. angiogram sheath injury
Where is the neurological lesion likely to be for paraparesis
Weakness of the lower limbs
Bilateral cerebral motor cortex e.g. parasagittal meningioma
Bilateral motor spinal tracts e.g. cord compression
Cauda equina e.g. lumbar intervertebral disc prolapse
Bilateral lumbosacral plexus e.g. GBS
Where is the neurological lesion likely to be for tetraplegia
Bilateral motor tracts of the cervical spinal cord
Peripheral nerves e.g. demyelinating disease, GBS
Where is the neurological lesion likely to be for proximal muscle weakness
NMJ e.g. myasthenia gravis, Eaton-Lambert syndrome
Muscle e.g. polymyositis, dermatomyositis or secondary to hyperparathyroidism or drugs e.g. statins
How can you differentiate between epilepsy and migraine
Both are associated with positive symptoms - tingling shaking, disturbances of vision
Migraine auras usually evolve over 20-30mins whereas epileptic seizures usually have onset over seconds
