Acute Weakness Flashcards
What are the signs of neuromuscular respiratory failure?
Often patient does not show obvious signs of respiratory distress…
- Orthopnoea - paralytic diaphragm means abdominal contents put pressure on thorax
- Paradoxical breathing (chest moves in during inspiration and out in expiration)
- Tachycardia
- Weak cough
- Rapid shallow breathing
Different patterns of weakness help to identify the level of the lesion, what does a monoplegia or hemiplegia indicate?
UMN lesion in the internal capsule or motor cortex.
Different patterns of weakness help to identify the level of the lesion, what does a diparesis and quadraparesis indicate?
Lesion in the spinal cord itself
Different patterns of weakness help to identify the level of the lesion, what does fatiguability indicate?
Lesion is at the level of NMJ e.g MG
Different patterns of weakness help to identify the level of the lesion, what does distal limb weakness indicate?
Lesion at the level of peripheral nerves
Different patterns of weakness help to identify the level of the lesion, what does proximal weakness indicate?
Lesion at the level of the muscle i.e. myopathy
What is the MRC scale for weakness?
0 = no contraction 1 = flicker of muscle contraction 2 = active movement without gravity 3 = active movement against gravity 4 = active movement against resistance and gravity 5 = normal contraction
Why is FVC measurement important in those with neuromuscular failure?
- FVC <15ml/kg is an indication to ventilate the patient
- Consider the need for additional respiratory support at FVC <30ml/kg
Vascular causes of weakness…
- Cerebral: stroke, TIA, SAH
- Spinal: stroke
Trauma causes of weaknesses…
- Cerebral: Haemorrhage, focal/ diffuse lesion
- Spinal: acute cord compression, cord transection
- Peripheral: compartment syndrome, penetrating injury
Infective causes of weakness…
- Cerebral: encephalitis, meningitis, abscess
- Spinal: abscess
- Peripheral: Lyme disease, HIV, Polio
- NMJ: Botulinum toxin
Autoimmune causes of weakness…
- Cerebral: MS
- Spinal: MS
- Peripheral: MS, GBS, sarcoid , vasculitis
- NMJ: Myasthenia gravis
- Muscle: myositis, dermatomyositis
Metabolic causes of weakness…
- Cerebral: encephalopathy (hepatic, Wernicke’s)
- Peripheral: Diabetes, renal failure, hypothyroid, B12/B1 deficiency, drugs, toxins
- Muscle: Hypothyroid, Cushing’s, rhabdomyolysis, drugs
Neoplastic causes of weakness…
- Cerebral: space occupying lesion
- Spine: malignant spinal cord compression
- Peripheral: Paraneoplasia
- NMJ: Lambert-Eaton syndrome (autoimmune disorder characterised by muscle weakness of the limbs)
- Muscle: Paraneoplasia
What are the main different types of stroke?
- Ischaemic stroke - broken down further according to Bamford Classification
- Haemorrhagic stroke - broken down into intracerebral and subarachnoid
What are the main causes of an ischaemic stroke?
Mainly caused by events that either precipitate artherosclerosis or lead to emboli formation:
Artherosclerosis: hypertension, high cholesterol, diabetes, smoking
Emboli formation: AF, DVT, carotid artery disease
*Most risk factors are common with cardiovascular risk factors
Bamford Classification of Strokes…
- Total anterior circulation strokes (TACS)
- Partial anterior circulation stroke (PACS)
- Lacunar stroke (LACS)
- Posterior circulation stroke (POCS)
How does TACS present?
- Hemiparesis +/- hemisensory loss
- Homonymous hemianopia
- Cortical dysfunction e.g. dysphasia, dysarthria
How does PACS present?
2/3 of: - Hemiparesis - Hemisensory loss - Homonymous hemianopia OR - Cortical dysfunction
How does LACS present?
- Pure motor, sensory or sensorimotor
- Ataxic hemiparesis
NO CORTICAL DYSFUNCTION
How does POCS present
- Cerebellar or brainstem syndrome: dizziness, diplopia, ataxia, dysarthria (CN involvement)
- Loss of consciousness
- Isolated homonymous hemianopia
How will a haemorrhagic stroke present
Usually presents with more global symptoms e.g.
- Drowsiness
- Headache
- Altered mental status
- Nausea and vomiting
- Seizures
What is the ROSIER score?
Recognition Of Stroke In the Emergency Room :
Used to identify actual stroke from stroke mimics
Score >0 = stroke likely
Score =/<0 = stroke unlikely - but cannot be ruled out
What is the NIHSS score?
NIH stroke scale (NIHSS) score = used to assess the severity of a stroke, has been found to correlate with clinical outcome when used within 48 hrs of presentation.
Grades: consciousness, orientation, gaze, visual fields, facial weakness, ataxia, sensation, dysarthria
Score < 4=favourable clinical outcome
What may a neurological exam reveal for a stroke patient?
- Limbs: initially flaccid then later spastic, weakness, absent reflexes
- Cranial nerve examination: facial paralysis, visual field defect (hemianopia)
What are the indications for urgent CT head in stroke patients?
- Likely candidate for thrombolysis
- On anticoagulation medication
- GCS <13
- Progressive symptoms
- Features of meningism
- Severe headache
Management of ischaemic stroke…
- Maintenance of homeostasis: SpO2 <95% ,blood sugar - normal levels, BP > 185/110
- Rule out haemorrhagic stroke with imaging (CT/ MRI)
- Presents < 4.5 hrs - thrombolysis with IV alteplase - 10% bolus, then 90% over 1hr infusion. This is followed by aspirin 24-48 hrs after
- Presents > 4.5 hrs - give 300mg aspirin - then continue for 2 weeks- switched to 75mg clopidogrel daily lifelong
- Physio and nutritional involvement: swallow assessment and nutrition screen using MUST tool
What are the contraindications for thrombolysis?
- Seizure
- Intracerebral/ subarachnoid haemorrhage
- INR > 1.7
- Uncontrolled hypertension
- GCS <8
- Abnormal BM
- Head injury
- Rapidly improving signs
Management of haemorrhagic stroke…
- CT/MRI shows bleeding in the brain
- Small bleeds = no requirement for neurosurgical involvement
Coagulation defects should be fixed - vitamin K or prothrombin complex
Large bleeds = neurosurgical involvement for drainage
Prevention of stroke…
Primary prevention:
- Modifiable risk factors: smoking, alcohol, obesity, diet
- Modifiable with drugs: hypertension, diabetes, hyperlipidaemia
Secondary prevention:
- Antiplatelet therapy: 1st line= clopidogrel
- BP control = ACEi and diuretic
- Statins for all patients
- Anticoagulation for AF
- Carotid endarterectomy (stenosis >70%)
What is a TIA?
Focal neurological deficit that resolves within 24 hours
Typical presentation of TIA…
- Unilateral weakness/ sensory loss
- Expressive dysphasia
- Amaurosis fugax (sudden transient loss of vision in one eye)
- Homonymous hemianopia
What is the ABCD2 score?
Used to risk stratify stroke in TIA patients:
- Age >60 =1
- BP > 140/90 =1
- Unilateral weakness =1 (+ speech disturbance =2)
- Duration 15-60 mins =1 (>60 mins=2)
- Diabetes = 1
Management of TIA
- Any pt with suspected TIA should have 300mg aspirin and be referred to TIA clinic
- ABCD2 score < 4 : seen in clinic within 7 days
- ABCD2 score =/>4: seen in clinic within 24 hrs
What malignancies most commonly metastasise to bone?
- Breast
- Prostate
- Lung
- Myeloma
- Lymphoma
What is the commonest region of the spinal cord affected by MSCC?
- Thoracic cord
Signs and symptoms of complete cord compression…
- Loss of all sensation below level
- Bilateral UMN weakness below level
- Bladder and bowel dysfunction
Signs and symptoms of anterior compression…
- Loss of pain and temp below level
- UMN weakness below level
- Bladder and bowel dysfunction
Signs and symptoms of posterior compression…
- Loss of vibration and proprioception
- Sparing of pain and temperature
Signs and symptoms of lateral compression…
- Contralateral pain and temp sensation loss
- Ipsilateral loss of vibration and position
- Ipsilateral UMN weakness.
Signs and symptoms of cauda equina…
- Back pain
- Saddle anaesthesia
- Urinary retention
- Loss of anal sphincter tone
Management of MSCC…
- Urgent MRI within 24 hrs
- 16-20mg dexamethasone PO (with PPI)
- Urgent referral to oncology MDT
- Radiotherapy to be given with 24h of MRI diagnosis
- Surgical decompression can be used with radiotherapy depending on the diagnosis.
What is the pathophysiology of MG?
Autoimmune disease where there are antibodies against nicotinic ACh receptors
What are the characteristic features of MG?
Muscle weakness with fatiguability, improving at rest
Clinical presentation of MG…
- Clinical presentation will range from mild weakness of limited muscle groups to severe weakness of multiple muscle groups
- Painless muscle fatigue e.g. voice becoming quieter the more it is used
- Muscles affected include finger flexors, bulbar weakness leading to dysphagia, facial muscle weakness
- Ptosis
- Diplopia
What are the main examination findings for MG?
Unlikely to find many positive findings unless movements are repeated which will lead to fatigue
What is the most common pattern of disease in MG?
- Ocular symptoms to generalised weakness within one year
- Takes around 40 years to progress to maximal weakness
What is the common method of fatality in MG?
- Neuromuscular respiratory failure which progresses eventually to acute respiratory failure
- Important to monitor tidal volume, vital capacity and blood gasses
What investigations can be carried out for diagnosing MG?
- First line= ice test, where ice is applied over eyelids for 3 mins showing improvement of ptosis
- Serology - nAChR and MuSK antibodies
- Neurophysiology - single fibre EMG and repetitive nerve stimulation
- Tensilion test - IV edrophonium used to provide improvement in muscle strength
- CT thorax to rule out thymoma
What are the risks of the tensilion test, what is an alternative?
Edrophonium carries the risk of causing bradycardia.
Pyridostigmine can be used instead.
Management of MG…
- 1st line = long acting Ach inhibitors e.g. pyridostigmine
- 2nd line = steroids e.g. prednisolone (tapered off)
- Immunosuppressants alongside steroids - azathioprine, methotrexate
- Thymectomy can be used in resistant disease where medical management has not worked (even in absence of thymoma)
What is a myasthenic crisis?
- Acute muscle weakness leading to respiratory failure which requires intubation
What is the management of a myasthenic crisis?
- Intubation and ventilatory support will be required early on
- Plasma exchange (50ml/kg for 10 days) and IV Ig (2g/kg for 5 days) with corticosteroids
What are the characteristic features of GBS?
- Acute, ascending, progressive polyneuropathy
- Causes weakness, parasthesia, diminished reflexes
- Usually infective prodrome affecting Resp/ GI tract 1-3 weeks before presentation
What are the common causative organisms of GBS?
- C jejuni
- EBV
- CMV
- Mycoplasma
Clinical features of GBS…
- Weakness starting in lower extremities with sensory deficit
- Other sx = neuropathic pain, autonomic sx, paraesthesia
- Signs on examination = hypotonia, altered sensation, reduced reflexes
- Max severity within 2 weeks
Investigations for GBS…
- Normally a clinical diagnosis - some tests can be helpful:
- Nerve conduction tests = definitive diagnosis as it shows slowing of conduction
- LP = elevated CSF protein
- Urinalysis, CXR, stool sample - find causative infection
- Spirometry - monitor resp muscle weakness and need for ITU admission
Management of GBS…
- IV Ig and plasma exchange
- VTE prophylaxis - as GBS patients are at greater risk
- 90% of patients make a full recovery
What are the different types of MND, and their clinical features?
- Amytrophic lateral sclerosis (ALS) = commonest form, both UMN and LMN signs : LMN = muscle atrophy , UMN= hyperreflexia, weakness of lower limbs and trunk
- Progressive bulbar palsy= affects lower cranial nerves leading to speech and swallowing problems
- Progressive muscular atrophy = LMN only, much slower progression than ALS
- Primary lateral sclerosis = UMN only
What is the usual presentation of ALS?
- Progressive muscle weakness - normally starting in the upper limbs
- Then spreads to bulbar, thoracic, abdominal muscles
- May initially look like clumsiness, foot drop may lead to tendency of tripping
- Bulbar symptoms = slurring of speech, tongue fasciculations, dysphagia
Indicative signs of MND…
- UMN and LMN signs
- Absence of sensory loss
- Asymmetrical distal weakness
- Fasciculations
How is the diagnosis of MND made?
*No specific diagnostic tests for MND
Presence of:
- LMN dysfunction evidenced by clinical or electrophysiological examination
- UMN dysfunction evidenced by clinical examination
- Progressive symptoms
Absence of:
- Electrophysiological evidence of other disease processes
- Neuroimaging evidence of other disease processes
Management of MND…
- Incurable condition - most patients survive 2-4 yrs post diagnosis
- Riluzole (glutamase releasing inhibitor)- shown to increase LE by few months
- Physiotherapy and speech therapy input
- Nutritional support - NG tube when body weight loss of >10%
- Respiratory support - NIV when resp function declines
- Symptomatic relief e.g. hysocine to stop drooling, pain relief, antidepressants
What is spinal cord infarction?
- Ischaemia to one portion of the SC caused by lack of blood supply from the arteries supplying the spine
- Usually caused by artherosclerosis within artery
- Aortic dissection is also a cause
How does spinal cord infarction present?
- Sudden back pain with tightness
- Followed by bilateral flaccid weakness and sensory loss
- Pain and temperature sensation lost (anterior spinal artery typically affected leading to anterior cord syndrome)
Management of spinal cord infarction…
- Treatment tends to be supportive
- Can sometimes treat the cause e.g. aortic dissection
What is critical illness neuropathy?
A syndrome of diffuse, flaccid muscle weakness that can occur in the critically ill patient - often seen in ICU settings.
Usually involves all extremities and the diaphragm.
How does critical illness polyneuropathy present?
- Muscle weakness seen in a generalised fashion- limb and respiratory muscles often affected
- Respiratory difficulties can prolong weaning process of ventilatory support
- Bilateral flaccid paralysis of arms and legs
