Neuromuscular + Peripheral Neuropathy Flashcards
In terms of NMJ conditions, which are pre-synaptic and which are post-synaptic
Presynaptic
- Lambert Eaton Myasthenic Syndrome (voltage gated calcium channel ab)
- Botulism: acetylcholine vesicle
Post synaptic
- Myasthenia gravis: acetylcholine receptors
- Organophosphate poisoning: acetylcholinesterase
Main characteristics of MG
- Post-synaptic antibody mediated disease (T cells)
- Associated with thymoma or thymic hyperplasia
- Ocular symptoms are the most common presenting symptom (diplopia, ptosis)
- Ptosis can be alternating
- Generalised weakness
- Fatigability
What conditions are MG associated with?
- Thymoma
- Thymic hyperplasia
- Hashimoto thyroiditis
- RA
- Sarcoidosis
- SLE
thymomas in 15%
autoimmune disorders: pernicious anaemia, autoimmune thyroid disorders, rheumatoid, SLE
thymic hyperplasia in 50-70%
What are the main clinical forms of MG
- Ocular MG: only the extraocular and/or eyelid muscles
- Generalised MG:
All skeletal muscles may be involved
Especially ocular, bulbar, limb and respiratory muscles - so difficulty standing up, climbing stairs, swallowing or chewing
Medications that should be avoided in MG
- Beta blockers
- Calcium channel blockers (verapamil)
- Aminoglycosides (eg: gentamicin) - especially out of the abx
- Fluoroquinolones (eg: ciprofloxacin)
- Tetracylcines (eg: doxycycline)
- Macrolides (eg: azithromycin)
- Phenytoin
- Lithium
- Magnesium
penicillamine quinidine, procainamide beta-blockers lithium phenytoin antibiotics: gentamicin, macrolides, quinolones, tetracyclines
Clinical features of MG
- Eye muscle weakness: most common initial symptom - ptosis, diplopia, blurred vision
- Bulbar muscle weakness: slurred speech, difficulty chewing and/or swallowing
- Proximal limb weakness: rising from chair, climbing stairs, brushing hair. Deep tendon reflexes not affected
- Resp muscle weakness: dyspnoea
- Muscle fatigability
Antibodies associated in MG
85% of patients have generalised myasthenia
- 85% are acetylcholine receptor (AChR) antibody positive
- 6-10% are muscle specific kinase (MuSK) ab positive
- Small group of seronegative can seroconvert in 1st year
15% of patients have ocular myasthenia
- 50% are ACHR antibody positive
- 66% of patients will progress to generalised within 2 years
- 90% of those who do not generalise within 2 years will remain ocular
(Most people will become generalised but a small subset remain ocular)
- AChR ab correlate with thymoma or thymic hyperplasia
- Antibody titres don’t correlate with clinical severity and no need to conduct follow up serology
- Ocular and generalised
MuSK Ab
- Non white, young, female
- Early onset
- Not related to thymoma/hyperplasia
- Generalised MG
- Severe weakness +/- atrophy
- Severe disease with respiratory and bulbar involvement
- Less fluctuation
- Poor response to treatment, good response to rituximab
LRP4 Ab: mild to mderate disease
MUSK and LRP4 are not associated with thymoma
Titin: late onset, severe thymoma
Titin also associated with myocarditis
Hanna Pearls
Acetylcholine receptor positive in 80% of patients
- 50% would have a thymoma - thymectomy
- 30% have hyperplasia of the thymus - for thymectomy if <55yo
- Can reduce immunotherapy after thymectomy
10-15% patients have MuSK antibody
- Patients do not have a thymoma and do not undergo a thymectomy
Titin Antibodies
- If this is positive, need to check anti-neuronal ab to check for paraneoplastic syndromes
-In patients who are titin ab positive, 100% patients will have a thymoma
Rare: can have seronegative MG so no antibodies
Investigations of MG besides Ab
- Ice Test: An ice pack is applied to the affected upper eyelid for 2-5 minutes. A positive test is the improvement of ptosis by > 2mm or more. This transient improvement in ptosis is due to the cold decreasing the acetylcholinesterase break-down of acetylcholine at the neuromuscular junction.
Single nerve fibre and repetitive nerve stimulation (electrodiagnostics)
- Single Fibre EMG: Best utilised for ocular MG
High sensitivity, low specificity, false positives
Repetitive Stimulation
- Repeated stimulation of nerve
- 10% decrement in amplitude is diagnostic - a smaller and smaller muscle response with each repetitive stimulus) is abnormal and indicates NMJ dysfunction.
- Greater decrement post exercise
- Generalised MG: Sensitivity 80%
- Ocular MG: 20%
Tensilon Test (edrophonium) 70-95% sensitivity
- Administration of edrophonium which is a short acting acetylcholinesterase inhibitor
- IV bolus given along with atropine at bedside (in case of myasthenia gravis)
- Assess if objective change in signs - normally would get better with repeated doses
- Sensitivity 60%, low specificity
- A patient suffering from myasthenia gravis experiences improvement in muscle strength and endurance with repetitive movements, while healthy persons do not feel any difference. The effects of edrophonium lasts around 10 minutes. The edrophonium allows accumulation of acetylcholine (ACh) in the neuromuscular junctions, and makes more ACh available to the muscle receptors, thereby increasing muscle strength in myasthenia gravis.
CT Chest for thymoma
Pathophysiology of MG
Normal:
Acetycholine fuse with the presynaptic membrane –> release of Ach in the synaptic cleft –> reversible binding of ACh to the nicotinic ACh receptor –> opening of receptor ion channel –> influx of ions –> depolarisation action potential and contraction of the muscle –> breakdown of Ach by cholinesterase and reuptake in the motor end plate
In MG
- autoantibodies compete with ACh for postsynatpic AChR –> ACh cannot bind –> receptor ion channel does not open –> no neuromuscular transmission
Treatment for MG
- Thymectomy
- Cholinesterase inhibitors: pyridostigmine (should be avoided in acute resp failure as it can increase resp secretions)
Pyridostigmine is a long-acting acetylcholinesterase inhibitor that reduces the breakdown of acetylcholine in the neuromuscular junction, temporarily improving symptoms of myasthenia gravis - If symptoms persist:
Steroids
Azathioprine: better than pred monotherapy but takes several months to become effective
Mycophenolate, tacrolimus, methotrexate
IVIG, plasma exchange, rituximab in refractory disease
Eculizumab: severe cases (C5 inhibitor)
Efgartigimoid: neonatal Fc receptor (FcRn) molecule that recycle IgG, extending its half life by about 4x that of other immunoglobulins. - For patients with MuSK ab - typically refractory to pyridostigmine, respond well to IVIG and plasmapharesis and rituximab.
Characteristics of myasthenia crisis
- Severe weakness with respiratory weakness/failure
- Causes: infection, surgery, pregnancy, medications (beta blocker, aminoglycosidesm calcium channel blockers, magnesium fluroquinolones)
- Tx; IVIG for 5 days, plasmapheresis, early intubation
Compare myasthenic crisis with cholinergic crisis
Myasthenic Crisis (too little acetylcholine) - mydriasis - Tachycardia - Cold and faint - Normal secretions - No fasciculations Tx: IVIG, plasmapheresis
Cholinergic crisis (too much acetylcholine due to too much cholinesterase inhibitors) - Miosis - Bradycardia - Fasciculations - Warm and flushed skin - Increased bronchial secretions - Abdominal cramps Tx; A cholinergic crisis should be treated by withdrawing all anticholinesterase medication, mechanical ventilation if required, and atropine i.v. for muscarinic effects of the overdose. The neuromuscular block is a nicotinic effect and will be unchanged by atropine.
Characteristics of lambert eaton myasthenic gravis
- Can be both autoimmune and paraneoplastic
- Paraneoplastic normally secondary to SCLC
- Non-neoplastic; HLAB8DR3
- Ab against voltage gated calcium channels, proximal weakness improves with exercise, exercise, dysautonomia
Clinical features of lambert eaton myasthenic gravis
Clinical triad of
- Proximal weakness which improves with exercise
Proximal LL –> proximal UL –> distal muscles –> oculobulbar
- Autonomic features: dry mouth, erectile dysfunction, constipation, urinary issues, orthostatic hypotension
- Areflexia
Ix of lambert eaton myasthenic gravis
- Voltage gated calcium channel ab
- Malignancy screen
- EMG: repetitive nerve stimulation results in incremental response
Tx of lambert eaton MG
- Tumour resection
- Amifampridine (3,4-diaminopyridine): blocks presynaptic potassium channel (blocks efflux of potassium ions) –> increase action potential duration/prolong duration of depolarisation –> increased presynaptic calcium concentrations
- Immunosuppression: IVIG, pred (in non paraneoplastic)
Contrast MG with LEMG
MG
- Associated disease: thymoma
- Starts with weakness of extraocular muscles, proximal weakness worsens with use
- Normal reflexes
- Repetitive nerve stimulation: decremental response
- Autonomic dysfunction: none
- Responds to cholinesterase inhibitors
LEMG
- Associated disease: small cell lung cancer
- Proximal limb muscle weakness that improves throughout the day
- Reduced/absent reflexes
- Repetitive nerve stimulation: incremental response
- Autonomic dysfunction: dry mouth, erectile dysfunction, constipation, urinary issues postural hypotension
- Amifampridine (3,4-diaminopyridine): blocks presynaptic potassium channel (blocks efflux of potassium ions) –> increase action potential duration/prolong duration of depolarisation –> increased presynaptic calcium concentrations
Characteristics of botulism
- Secondary to clostridium botulinum
- Inhibit presynaptic acetylcholine release
Foodborne Botulism
- Ingestion of botulinum toxin
- Incubation mean 2 days
- N+V
- Symmetric descending flaccid paralysis
- Autonomic involvement: dry eyes, dry mouth, paralytic ileus, urinary retention
- Internal and external ophthalmoplegia
Internal: pupillary muscles, dilation of pupil, and fixed
External: paralysis of extraocular muscles - can’t move eyes
If there is internal + external ophthalmoplegia think toxin! - Mentation and reflexes preserved
Mx
- Removal of unabsorbed toxin only considered if ileus present
- Avoid aminogycoside use as death of clostridum leads to more toxin being produced
- Equine antitoxin
Prognosis
- Recovery over months
- Main complication are immobility and intubation
External ophthalmoplegia means paralysis of the extraocular (extrinsic) muscles that move the eyes. Internal ophthalmoplegia means paralysis of the intrinsic (internal) eye muscles that control pupil size and accommodation (focusing).
Characteristics of GBS (AIDP)
Acute idiopathic demyelinating polyradiculoneuropathy
- Characterised by ascending symmetrical flaccid paralysis with areflexia
- Albuminocytologic dissociation, characterised by elevated protein levels and normal cell count in CSF
Cause of GBS
- Occur usually 4 weeks after an upper respiratory tract infection or GIT infection
- Most commonly associated with campylobacter jejuni + CMV
Other causes include: - Bacterial: Mycoplasma pneumoniae Viral: CMV, Zika virus, EBV, HIV, influenza, covid 19 - ZIKA - 2 weeks post COVID 18 - Post immune checkpoint inhibitors - ?vaccinations
Pathophysiology of GBS
Humorally mediated rather than T cells
- Postinfectious autoimmune reaction that generates cross-reactive antibodies (molecular mimicry)
- Infection triggers humoral response → formation of autoantibodies against gangliosides (e.g., GM1, GD1a) or other unknown antigens of peripheral Schwann cells → immune-mediated segmental demyelination → axonal degeneration of motor and sensory fibers in peripheral and cranial nerves (CN III–XII)
Clinical features of GBS
- Symmetrical ascending flaccid paralysis
- Reduced/absent reflexes
- Autonomic dysfunction: arrhythmia, void dysfunction, intestinal dysfunction,, postural hypotension
Autonomic symptoms are common in GBS. The most frequently encountered are tachycardia and urinary retention. Although autonomic dysfunction may manifest as hypertension, hypotension, bradycardia, or ileus, these are not as commonly seen. - Respiratory muscle involvement
- Sensory deficit rare
- Lower back pain
- Symptoms peak at 4 weeks
Subtypes and variants of GBS
- AIDP
- acute variant
- Associated with campylobacter jejuni + CMV
- Ascending flaccid paralysis, autonomic neuropathy, peak at 4 weeks
- IVIG, plasmapheresis - CIDP
- Chronic variant > 8 weeks
- Sensory symptoms and proximal weakness more common - proximal and distal weakness
- Reduced reflexes
- Milder phenotype, rarely have resp involvement/intubation
- Anti-GM1 ganglioside autoantibodies
- Clinical features > 8 weeks
- Glucocorticoids, azathioprine, cyclophosphamide, plasmapharesis, IVIG, ritux for Ab positive disease (better outcomes with early treatment) - Miller Fisher syndrome
- Limited variant of GBS characterised by cranial nerve involvement
- Autoantibodies directed against ganglioside Gq1b, GTa
- Ophthalmoplegia, ataxia, areflexia
- IVIG - Multifocal motor neuropathy (MMN)
- Variant of GBS affecting the motor neurons - asymmetric pure motor weakness
- Onset is usually in the upper extremities
- DDx for AML
- Anti- GM1 ganglioside autoantibodies
- Usually normal protein levels in CSF
- Asymmetric paralysis and areflexia
Deep tendon reflexes are usually decreased but typically intact in unaffected areas
- IVIG
- Steroids can worsen condition. - Acute motor axonal neuropathy
- Abrupt onset variant of GBS
- Affects motor nerve fibres with variable severity and spares sensory fibres
- Typically occurs after campylobacter jejuni, against GM1 ganglioside like epitopes
- Acute paralysis
- Areflexia without sensory loss
- IVIG, plasmapheresis
Ix for GBS
Bloods
- Elevated LFT in 30%
- Elevated CK
- Serology for C jejuni, HIV, CMV, EBV
CSF
- Albuminocytologic dissociation, high protein levels and normal cell count
- Elevation may be delayed it taken too early
Forced vital capacity, <1L = ICU
NCS
- Decreased nerve conduction velocity due to demyelination /conduction block
- Prolonged F wave latency
EMG: denervation, demyelinating pattern
ECG: autonomic cardiac dysregulation - impaired heart frequency variation
Autoantibodies associated with the different variants of GBS
- CIDP: Anti GM1
- Miller Fischer: GQ1b
- Acute motor axonal neuropathy: GD1a, GM1
- Sensory GBS: GD1B
- Bulbar Palsy: GT1a
- Multifocal motor neuropathy (purely motor): GM1
- Bickerstaff Brainste, Encephalitis: GQ1b
- Acute Motor Axonal Neuropathy: GD1a, GM1
Tx of GBS
Tx of CIDP
GBS/AIDP
IVIG
- No benefit of PEX followed by IVIG
Plasmapheresis:
- removes autoantibodies, immune complexes, complement and cytokine
- Within 2-4 weeks of onset
- Should be wary in people with autonomic instability
Steroids DO NOT work well - lead to worse outcome
CIDP
- IVIG, plasmapheresis
- Can use steroids
Complications of GBS
- Respiratory paralysis
- Pulmonary infection/embolism
- Cardiac dysfunction
- Unable to walk unaided
Difference between small fiber and large fiber neuropathies
Small Fibre Neuropathies
- Involve small, unmyelinated nerve fibres
- Affect pain + temperature sensation and autonomic function
Large fibre neuropathies
- Associated with loss of joint position/proprioception, vibration, pressure and sensory ataxia (touch).
Peripheral neuropathy Ix
FBC, EUC, CMP, LFT, CRP, ESR Protein electrophoresis with immunofixation TFT Glucose Vitamin B12
Benefits of EMG
Can confirm presence of neuropathy
Differentiate between axonal or demyelinating
Distinguish neuropathy from myopathy and radiculopathy from plexopathy
Types of nerve fibres
A fibres: myelination present, involved in sensory (touch, vibration, pain, temperature)
B fibres: myelinated, preganglionic sympathetic fibres
C fibres: absent myelination, involved in visceral pain, post-ganglionic sympathetic fibres
Types of Nerve Damage
Neurapraxia = focal demyelination
- Compression injury causing temporary disruption of nerve conduction
- The whole nerve remains structurally intact
- Good prognosis with complete recovery of nerve function
- Results in focal demyelination, no loss of axonal integrity
- Weakness and sensory loss are due to conduction block which can be confirmed with electrodiagnostic studies (NCS or EMG)
- If axon distal to injury is intact = nerve continuity across the site of injury = excellent recovery days-weeks-maximum months
Axonotmesis = axonopathy
- Caused by crush injury, nerve stretch (MVA, fall) or percussion injuries (eg: gunshot wounds)
- Axon damaged but perineurium and epineurium intact
- The axon is locally but irreversibly damaged and the myelin sheath is similarly involved
- Leads to wallerian degeneration : axon and myeline sheath distal to injury degenerate
- Prognosis depends on many factors with regards to nerve, anatomy, function sensory vs motor = essentially partial recovery, but much longer than neurapraxia
Neurotmesis = complete disruption of entire nerve, irreversible damage of axon and myelin/complete nerve transection
- Caused by severe lesions eg: sharp injuries, traction injuries or exposure to neurotoxic substance
- The axon, myelin sheath and surrounding stroma are all irreversibly damaged
- No regeneration unless surgery re-anastomosis
Brachial plexus injuries
- Complete lesions
- Upper Trunk/Erbs/C5-C6
- Lower Trunk/Klumple/C8-T1
Occur rarely only secondary to trauma and malignancy.
Complete lesions
- Motor: LMN weakness affecting the whole limb
- Sensory: sensory loss of the whole limb
- Other: horners
Upper Trunk/Erbs/C5-C6
- Cause: excessive lateral flexion of neck, trauma, birth injury
- Motor: weakness of muscles in C5/6/palsy of axillary, suprascapular and musculocutaneous nerve
- leading flexed wrist with an extended forearm and internally rotated and adducted arm (waiter’s tip position)
Weak: biceps brachii, infraspinatus, wrist extensors, deltoid, supraspinatus, waiter’s tip posture
imagine BIRDS eating hERBS served by a waiter
- Sensory: loss over lateral aspect of arm and forearm
- Winged scapula
Lower Trunk/Klumple/C8-T1
- Cause: hyperabduction of the arm, compression f the lower trunk of brachial plexus by pancoast tumour, cervical rib
- Motor: true clawhand with paralysis of all intrinsic muscles (thenar, hypothenia, lumbricals, interossei) - median, ulnar
- Sensory: loss along medial aspect of hand and forearm
- Others: Horner’s
Radial Nerve
- Normal function
- Radial nerve palsy
Radial Nerve (C5/T1) - Motor: extension of everything
Radial Nerve Radiculopathy:
Cause
- Axilla: from crutch use, saturday night palsy
- Mid arm: midshaft fracture of humerus
- Wrist: radial fracture, wearing tight bracelets
- Motor: wrist drop due inability to extend at the wrist and fingers
- Sensory:
Dorsal: lateral 2.5 fingers excluding tips of 2nd and 3rd fingers, anatomical snuffbox
Palmar: 1st webspace
Proximal Lesion: complete loss of motor and sensory Distal lesion (radial tunnel syndrome): partial loss of motor function, preservation of sensory function
Axillary Nerve injury
Axillary C5/6
Cause:
- Anterior shoulder dislocation
- Fracture of surgical neck of humerus
Motor Deficit
- Paralysis of the deltoid muscle –> impaired arm abduction
- Paralysis of the teres minor muscle –> impaired external rotation of the arm
- Deltoid atrophy
Sensory
- Deltoid region
Musculocutaneous
Musculocutaneous C5-7
Normal function:
Motor: elbow flexion
Sensory: lateral forearm
Cause: trauma, upper trunk compression (erb balsy)
Motor:
- Paralysis of brachialis: impaired elbow flexion
- Paralysis of biceps brachii: impaired forearm supination
- Reduced biceps reflex
Sensory: lateral forearm from the elbow to the base of the thumb
Median Nerve
Median Nerve C5-T1
Normal
Motor: wrist flexion, finger flexion, lumbricals.
- innervates muscles of the anterior foream, supplies almost all the flexors of the wrist and fingers except the flexor carpi ulnaris and medial half of flexor digitorum profundus (ulnar does medial 2 fingers)
- Supplies thenar muscles and lateral 2 lumbricals (LOAF)
Lateral 2 lumbricals: MCPJ flexion, IPJ extension of 2nd and 3rd digits
Opponens pollicis brevis: opposes thumb
Abductor pollicis brevis: abducts thumb
Flexor pollicis brevis: flexes thumb
Injury
- Proximal: supracondylar fracture of humerus above the anterior interosseus nerve origin
- Distal: carpel tunnel compression below the anterior interosseus nerve origin
Motor:
- atrophy of thenar muscles
- Impaired flexion of wrist, thumb, index and middle finger.
- Proximal injury: Hand of benediction (when trying to make a fist) - unable to flex thumb, index and middle finger
- Distal injury: median claw (when extending the fingers) -
Median Claw: paralysis of lateral lumbricals causes permanent flexion of the index and middle finger at the DIP/PIP – can’t EXTEND 2nd and 3rd dingers
- pen touch test for loss of abductor pollicis brevis with lesion at or above wrist
- Deep injury to the wrist or forearm impairing the thenar muscles/superficial palm laceration: ape hand, impaired thenar muscles, impaired flexion/abduction and opposition of thumb.
- Positive pinch sign in anterior interosseus nerve syndrome
Sensory:
Proximal + Distal
- Thenar eminence
- Palmar aspect of thumb, index, middle finger and lateral ring finger (lateral 3.5)
- Dorsal: loss of sensation over tips of the lateral 3.5 fingers
Ulnar nerve
Normal Function
- Motor: finger abduction, finger adduction, digits 4 + 5 ulnar part of flexor digitorum profundus
2 muscles of the anterior forearm:
Flexor carpi ulnaris – flexes and adducts the hand at the wrist
Ulnar (medial) half of flexor digitorum profundus - flexes the 4th and 5th fingers at the distal interphalangeal joint
ntrinsic muscles of the hand except the LOAF muscles which is supplied by the median nerve
Hypothenar muscles (group of muscles associated with the little finger): flexor digiti minimi brevis, abductor digiti minimi, opponens digiti minimi – control movement of the 5th digit
Medial two lumbricals/3rd and 4th lumbricals - MCPJ flexion, IPJ extension for 4th and 5th finger
Adductor pollicis – adducts the thumb
Cause
-Proximal:
Fracture of the medial epicondyle of the humerus (funny bone)
Cubital tunnel syndrome
- Distal
Ulnar tunnel syndrome (from cycling, ganglion cysts)
Injury
Damage at the Elbow
- Motor: All the muscles innervated by the ulnar nerve are affected
- Sensory: All sensory branches are affected
Damage at the Wrist
- Motor: all intrinsic hand muscles affected except LOAF
- Sensory: variable sensory deficit, depending on whether palmar/superficial branch or dorsal branch is affected
Motor
- Atrophy of the hypothenar muscles
- Claw hand deformity/ulnar claw – clawing of the 4th and 5th fingers (mainly in distal nerve injuries)
- Hyperextension of 4th and 5th MCP and flexion of 4th and 5th PIP + DIP
Usually worse when the lesion occurs at the wrist as opposed to the elbow due to greater muscle imbalance. Wrist lesions usually present with weakness of the 3rd and 4th lumbrical muscles while the flexor digitorum profundus is spared (unlike the elbow where both are affected)
Wrist: FDP not affected, medial lumbricals affected - 4th and 5th DIP more flexed
Distal Ulnar Nerve Injury: can’t EXTEND 4th and 5th fingers
Elbow: FDP affected, medial lumbricals affected - less flexion of 4th and 5th DIP
Proximal Ulnar Nerve Injury: can’t FLEX 4th and 5th fingers - Atrophy of the interosseous muscles
Inability to abduct and adduct fingers (paralysis of interosseous) – patient cannot grip paper placed between fingers - Inability to adduct thumb leading to positive Froment’s sign (due to paralysis of adductor pollicis)
The patient is asked to hold a piece of paper between the thumb and index finger, as the paper is pulled away
They should be able to hold the paper there with no difficulty (via adduction of the thumb).
A positive test is when the patient is unable to adduct the thumb. Instead, they flex the thumb at the interphalangeal joint to try to maintain a hold on the paper.
-Sensory
Loss of sensation over dorsal and palmar surface of the medial one and half fingers
Upper limb reflexes
- Biceps: C5/C6, musculocutaneous
- Brachioradialis: C5/C6, Radial
- Triceps: C7/8, Radial
What is the motor function of inferior gluteal
L4/5
Hip extension
Nerve roots of foot inversion and eversion
Inversion: L4/5
Eversion: L5/S1
Injury to lateral femoral cutaneous nerve (meralgia paresthetica)
L2/L3
Compressive neuropathy of the lateral femoral cutaneous nerve that causes isolated anterolateral thigh numbness without weakness.
What is ramsay hunt syndrome
Ramsay Hunt syndrome (herpes zoster oticus) is caused by the reactivation of the varicella zoster virus in the geniculate ganglion of the seventh cranial nerve.
Features
- auricular pain is often the first feature
- facial nerve palsy
- vesicular rash around the ear
- other features include vertigo and tinnitus
Management
- oral aciclovir and corticosteroids are usually given
Treatment of bells palsy
Steroids within 72 hours of symptoms onset
Difference between axonal and demyelinating diseases
NCS can help differentiate between axonal and demyelinating conditions
Demyelinating
- Weakness without atrophy
- Length independent distribution - proximal dominant
- Asymmetric/patchy distribution
- Loss of proximal reflexes
- Myokymia of the lid is a unilateral and uncontrollable lid twitch or tic that is not caused by disease or pathology.
- Sensation: usually mild prominent propioception/vibration, pain and temp not lost alone
- Autonomic involvement; only in GBS or autoimmune dysautonomia
- NCS: increase in latency, reduction in conduction velocity
- Recovery: rapid
Causes of Demyelinating
- Genetic: CMT1, HNPP
- Immune mediated: CIDP, GBS, MMN (Multifocal Motor Neuropathy)
- Paraproteinemia
- HIV, leprosy, cryoglobulins (hep C)
- Diphtheria
- amiodarone
- Charcot marie tooth 1
Axonal
- Ankle jerk reduced, knee jerk preserved (length dependent loss)
- Length dependent distribution
- Often symmetric
- Early wasting
- Distal > proximal
- UL affected when symptoms extend to the knees
- Sensation: depending on type of fibres involved, pain/temp/light touch/vibration
- Autosomal involvement: yes with small fibre loss (diabetes, amyloidosis)
- NCS: reduction in amplitude
- Recovery: slow
Causes of Axonal
- Charcot marie tooth type 2
- Diabetes
- Uremic neuropathy
- Toxic, chemotherapy
- Alcohol
- Vasculitis
- Vitamin B 12 deficiency
