Neuro - Four Limb Weakness Flashcards
Describe Guillain-Barre Syndrome and it’s pathogenesis?
GBS = is a peripheral neuropathy involving acute immune mediated demyelination of the PNS often triggered by an infection (classically Campylobacter jejuni)
Pathogenesis:
- Antibodies produced to fight infective pathogens cross-react with gangliosides (molecules present on nerve cell surface) in the PNS
- Technically GBS is a poly radiculo-neuropathy
Note: GBS was long thought to be monophasic, but rarely pts have been known to have recurrent episodes of GBS (episodes tend to be of different strengths and very far apart in time)
What are the features of Guillain-Barre syndrome?
Features:
- Progressive symmetrical weakness of all four limbs
classically - ascending weakness (lower limbs first) and proximal muscles before distal - Distal paraesthesia (precedes weakness but sensory loss on examination tends to be mild)
- Areflexia
- Dysautonomnia e.g. sinus tachycardia, urinary retention, variable BP, postural hypotension, ileus (obstruction due to ↓ peristalsis)
- Hx of recent infection e.g. gastroenteritis, URTI or influenze-like illness
- Pain - back / legs most common (the combo of pain + paralysis can be misinterpreted as cord compression)
- Breathlessness (30%) - due to respiratory muscle weakness, can require ICU / mechanical ventilation
- Slurred speech - due to facial / oropharyngeal weakness
- Cranial nerve involvement e.g. diplopia, extraocular or facial weakness (commonly occurs after limb/trunk involvement be can precede)
- Papilloedema (rare - secondary to ↓ CSF resorption)
What investigations would you do for a patient with suspected Guillain-Barre syndrome (GBS)?
Beside:
- CN exam
- Upper + lower limb neurological exam
- Cardio / Resp / Abdo exam (to exclude other causes)
Bloods:
- FBC
- check for infection (↑ WBC) and macrocytic anaemia (B12 deficiency)
- U+Es, LFTs, Ca2+, phosphate, Mg2+
- electrolyte derangement can contribute to limb weakness
- CRP & ESR
- inflammatory markers (infection)
Other:
- Lumbar puncture - ↑ protein + normal WBC (this is called albuminocytologic dissociation) seen in 66%
- Spirometry - investigate breathlessness (FVC < 1L = concern, consider ICU)
- CXR
- as GBS progresses pts become breathless due diaphragm being affected, CXR excludes other causes
- ECG - investigate breathlessness
- Nerve conduction studies (maybe)
What can commonly precipitate GBS?
The acute infectious illness precipitating GBS is often viral, but can be bacterial
Viral:
- CMV (cytomegalovirus)
- EBV (Epstein-Barr virus)
- Hepatitis B or C
- HIV
- H1N1 (Swine flu - influenza A subtype)
Bacterial:
- Campylobacter jejuni (most common)
- Mycoplasma species
Systemic illnesses:
- Hodgkin’s lymphoma
- Hyperthyroidism
There are many variants of GBS based on symptoms, one of these is Miller-Fisher syndrome (MFS).
What are the features of MFS?
Features:
Triad:
- Opthalmoplegia
- Areflexia
- Ataxia
Eye muscles affected 1st (~30% develop extremity weakness as well)
Descending paralysis as opposed to asending as seen in other GBS forms
Anti-GQ1b antibodies present in 90%
How are patients with suspected GBS managed?
WITHOUT IgA deficiency or renal failure:
1st line = IVIG (intravenous imunnoglobulin) OR plasmapheresis - they have equal efficacy so choice depends on institution
- IVIG 400mg / Kg / day for 5 days
- Complication rates are lower with IVIG than plasmapheresis
WITH IgA deficiency or renal failure:
1st line = plasmapheresis
In IgA deficient pt the IVIG can cause anaphylaxis
Other:
- Repeat spirometry for FVC measure –> if declining then transfer to ICU
- Thromboprophylaxis - pts often in bed for extended period (especially if admitted to ICU) - use graded compression stockings TEDs (thrombo-embolic deterrent) + LMW heparin
Name a differential that can produce a similar picture to GBS symptoms?
What are the main features of this condition?
Transverse myelitis = inflammation of both sides of spinal cord at one level, often damaging myelin sheaths
- Motor weakness + altered sensation - can be in all 4 limbs (cervical cord) as in GBS - BUT motor / sensory loss if often asymmetrical
- Autonomic dysfunction - urinary incontinence / urgency / frequency, bowel incontinence or constipation
- UMN signs - hyper-reflexia, dorsiflex Babinski, spasticity (↑ tone, velocity-dependent ↑ in stretch reflexes) - note: very acute cases can exhibit areflexia + flaccidity called ‘spinal shock’, this will pass and become UMN signs
- Hx of recent infectious illness / vaccination
Name some contra-indications to doing a lumbar puncture.
Cardio-respiratory compromise - the fetal position (ideal position) for an LP can make breathing difficult
↑ ICP - as an LP can cause spinal decompression and induce cerebral herniation through the foramen magnum
Coagulopathy / anticoagulation - this ↑ the risk of spinal haematoma
Previous lumbar surgery - consult interventional radiologist
What elements are measure on an LP and what are their normal ranges?
Opening pressure (8 - 20 cm CSF)
- Result is only valid in the lateral recumbent position
- ↓ pressure = CSF leak or recent LP
- ↑ pressure = meningitis, tumour, intracranial haemorrhage, IIH (idiopathic intracranial hypertension)
CSF appearance:
- Clear = normal
- Cloudy or purulent = meningitis
- Bloody = traumatic tap or subarachnoid haemorrhage
RBC count (< 5 cells/mm3) - ↑ can be due to puncturing a vessel during procedure or subarachnoid haemorrhage
WBC count (< 5 cells/mm3)
- puncture of small vessel will artificially ↑ WBC count
- ↑ neutrophils = bacterial infection
- ↑ lymphocytes = viral e.g. HIV, TB or fungal
Protein (0.2-0.4 g/L)
- ↑ can be due to; meningitis, GBS, MS, brain abscess, intracranial haemorrhage, neoplastic disease
Glucose (always interpret alongside blood glucose):
normal = 40-60% of blood glucose
- < 40-60% of blood glucose = CNS infection; bacterial, fungal or TB (not characteristically viral)
Extra tests:
- Microbiological stains
- Culture + sensitivity
- Viral / bacterial PCR e.g. type of bacteria in bacterial meningitis
- Oligoclonal bands - presence = synthesis of IgG in CNS e.g. multiple sclerosis (not specific for this though)
What is the prognosis of GBS like?
it varies depending on GBS type but answer is general
Prognosis:
- Mortality 3-5%
- Severe disability 15%
- Recovery 80% within 6 months
What is myasthenia gravis?
Myathenia Gravis:
Is an autoimmune disorder against NMJ nicotinic acetylcholine receptors
Women > men (2:1)
Antibodies to nicotinic ACh receptors (85-90% cases, antibodies less common in MG limited to extra-ocucular muscles)
Associated with:
- Thymomas (15-20%) - benign or malignant tumour of thymal epithelial cells - for this reason after diagnosis with myasthenia gravis many pts have CHEST CT to look for thyomas
- Thymic hyperplasia (50-70%)
- Autoimmune disorders; pernicious anaemia, thyroid (Hashimoto’s), RA, SLE etc.
What are the features of myasthenia gravis?
Proximal fatiguable limb weakness
- Fatiguability = with prolonged activity the weakness becomes worse and is improved after rest
- Proximal muscle weakness = ‘rising from seat’, ‘climbing stairs’ and ‘combing hair’ is difficult
- Exhibits diurnal variation (better in morning than evening)
Ptosis
Diplopia - due to extraocular muscle weakness
Dysarthria - if oropharyngeal muscles are affected (characteristic nasal speech)
Dysphagia - if oropharyngeal muscles are affected (difficulty chewing/swallowing)
Facial paralysis - if facial muscles affected (characteristic flattened / transverse smile)
SoB (less common)
NORMAL:
- Reflexes
- Sensation
- No muscle wasting
- Autonomic function
A 25 year old man presents to A+E with a 3 day history of weakness and numbness affecting the legs and feet. Examination reveals normal cranial nerves and upper limbs. In the lower limbs there is increased tone, brisk reflexes, upgoing plantars and grade 4 power in all muscle groups tested. Sensation to pinprick is altered throughout the legs and pelvic area. Joint position sense seems intact.
Choose the most useful diagnostic test.
- Vitamin B12 level
- MRI thoracic spine
- MRI brain
- MRI lumbrosacral spine
- FBC
MRI thoracic spine
- symptoms and signs are compatible with a thoracic myelopathy
- MRI scan of the lumbosacral spine would miss the pathology as the signs clearly suggest UMN disease (the spinal cord terminates at L1)
What is central cord syndrome (CCS)?
Central cord syndrome
- CCS = commonest cervical spinal cord injury
- Commonly caused by neck trauma
- More likely in elderly with cervical spondylosis
Features:
- Weakness - upper limb much worse than lower
- Altered sensation - varied picture but upper limb tends to be worse than lower
- UMN signs
What are the features of Cauda Equina syndrome?
Cauda Equina:
- Lower back pain / sciatica-like pain
- Urinary retention –> overflow incontinence
- Early presentation is of difficulty starting / stopping urine flow - ↓ perianal sensation (saddle anaesthesia) - S3 - S5 dermatomes
- ↓ anal tone on PR exam
- Absent ankle reflex bilaterally
- Sexual dysfunction
