JC32 (Medicine) - Neuropathy, Myopathy Flashcards
List 5 major categories of generalized weakness
- Polyneuropathies
- Muscular Dystrophies
- MG
- Inflammatory Myopathies
- Floppy infant syndrome
Ddx peripheral neuropathies/ Polyneuropathies
Peripheral neuropathies
- Hereditary neuropathies
- GBS,
- Toxins
- DM,
- uraemia,
- Vit B12 def,
- paraproteinaemia and immune neuropathies
- CIDP
Ddx NMJ diseases with generalize weakness
Pertinent features
- * MG**
- * LEMS**
Ddx muscle diseases with generalize weakness/ Myopathies
- Dystrophies,
- congenital myopathy, channelopathy
- Myositis,
- toxic or metabolic myopathy,
- rhabdomyolysis
Symmetrical, Fluctuating proximal weakness + ocular and bulbar involvement
Normal reflexes
No wasting
Most likely lesion? Ddx
NMJ disease
e.g. MG, LEMS
Symmetrical distal weakness
Absent or hyporeflexia
Muscle wasting
Non-dissociated sensory involvement
Trophic changes
Steppage gait
Sensory symptoms/ pain
Ocular-sparing
Autonomic signs
Most likely lesion? Ddx
Peripheral neuropathies
- Hereditary neuropathies
- GBS,
- Toxins
- DM,
- uraemia,
- Vit B12 def,
- paraproteinaemia and immune neuropathies
- CIDP
Symmetrical proximal weakness
Fasciculation and wasting present
Reflexes intact
Waddling gait
+/- ocular and bulbar involvement
+/- pain and tenderness
Most likely lesion? Ddx
Muscle diseases
- Dystrophies,
- congenital myopathy, channelopathy, mitochondrial disease
- Myositis,
- toxic or metabolic myopathy,
- rhabdomyolysis**
Asymmetrical weakness
Involves UL extensors and LL flexors
UMN signs - hypertonia, Babinski, Hoffman, Hyperreflexia
Dissociated sensory involvement
Spastic/ plegic gait
Sensory and bulbar symptoms
+/- Sphincter dysfunction
Most likely lesion
CNS lesion
Cervical myelopathy, Brainstem pathology
Investigation for CNS lesion causing generalize weakness
CT/MRI brain
LP and CSF analysis
Investigation of peripheral nerve lesion with generalize weakness/ polyneuropathies
- Electrophysiological studies - Nerve Conduction Study
- R/o systemic diseases: e.g. HbA1c for DM, Vit B12 for SCCD, TFT for thyroid proximal myopathy
- Lumbar Puncture and CSF analysis
- Nerve biopsy (rare)
- Genetic tests
Investigations for NMJ diseases **
Repetitive nerve stimulation test
Tensilon test
Anti-AChR
Investigations for muscle diseases
Muscle Enzymes: CK, lactate
Electrophysiological studies - EMG
MRI
Muscle Biopsy
Genetic tests
Differentiate radiculopathy, plexopathy, and neuropathy with subtypes
□ Radiculopathy involving nerve roots
□ Plexopathy involving nerve plexus
□ Neuropathy involving nerves
→ Mononeuropathy: only one nerve affected
→ Mononeuritis multiplex: multiple sequential mononeuropathies
→ Polyneuropathy: symmetrical involvement of all/most peripheral nerves
4 key questions to classify exact type of peripheral nerve lesion
□ Time course: acute, subacute, chronic, relapsing
□ Distribution: generalized, focal; symmetrical, asymmetrical
□ Type of fibres involved:
→ Large (mostly -ve symptoms) vs small fibers (mostly +ve symptoms)
→ Motor, sensory, autonomic, mixed
□ Pathology:
→ Axonal: damage to nerve cell
→ Demyelinating: damage to Schwann cells making up the myelin sheath
Motor features of peripheral nerve lesion
LMN Motor: weakness, wasting, fasciculation, hyporeflexia
→ Distal weakness: difficulty in tip-toeing, foot drop, ↓manual dexterity
→ Proximal weakness: difficulty in climbing stairs, combing hair, standing up from siting position
Sensory features of peripheral neuropathy
Sensory:
→ Large, myelinated fibres: loss of touch/proprioception (-ve) or pins-and-needle (+ve)
→ Small, unmyelinated fibres: loss of pain/temperature (-ve) or pain (+ve)
Autonomic features of peripheral neuropathy
Autonomic: rarely occurs alone, usually complicates other neuropathies
→ Postural hypotension → postural BP for all neuropathy to detect autonomic involvement
→ Disturbance in sweating, cardiac rhythm, GI/bladder functions, sexual function
Trophic changes asso. with peripheral neuropathy
Trophic changes: disuse atrophy, hair loss, brittle nails, trophic ulcers, Charcot’s joints
Ddx Nerve thickening syndromes
leprosy, acromegaly, HMSN, CIDP, neurofibromatosis
Main causes of mononeuropathy
□ Entrapment/ Compressive mononeuropathy: damage to a nerve where it passes through a tight space
□ Trauma
□ Other focal lesions, eg. granulomatous inflammation
Entrapment neuropathy
Predisposing factors
Management
Predisposing factor:
→ Generalized soft tissue swelling, eg. acromegaly, myxedema, pregnancy
→ Others: DM, excess alcohol/toxins, genetic syndromes
Mx: remove entrapment by avoiding precipitating factors or surgical decompression
Median nerve entrapment
- Site
- Symptoms
- Muscle weakness
- Area of sensory loss
- Site - at wrist, carpal tunnel syndrome
- Symptoms - Pain and paresthesia at palmar hand, may extend to arm and shoulder
- Muscle weakness - Abductor pollicis brevis
- Area of sensory loss - Lateral palm and thumb, index, middle and lateral half of 4th finger
Ulnar nerve entrapment
- Site
- Symptoms
- Muscle weakness
- Area of sensory loss
- Site - Elbow at Cubital tunnel at medial epicondyle
- Symptoms - Paraesthesia on medial border of hand, wasting and weakness of hand muscles
- Muscle weakness - All hand muscles except abductor pollicis brevis
- Area of sensory loss - Medial palm and little finger + medial half of 4th finger
Radial nerve entrapment
- Site
- Symptoms
- Muscle weakness
- Area of sensory loss
- Site - area of frosche, radial tunnel syndrome
- Symptoms - weakness of wrist and finger extension, precipitate by abnormal position (e.g. arm over back of chair)
- Muscle weakness - Wrist and finger extensors, supinators
- Area of sensory loss - Dorsum of thumb
Common peroneal nerve entrapment
- Site
- Symptoms
- Muscle weakness
- Area of sensory loss
- Site - proximal fibula fracture/ entrapment/ trauma to head of fibula
- Symptoms - Foot drop
- Muscle weakness - Dorsiflexion and eversion of foot
- Area of sensory loss - Dorsum of foot, web between 1st and 2nd toe
Lateral cutaneous nerve of thigh
- Site
- Symptoms
- Muscle weakness
- Area of sensory loss
- Site - hypertrophy or abnormal piriform muscle compressing onto nerve from top
- Symptoms - Tingling and dysaesthesia on lateral border of thigh
- Muscle weakness - None
- Area of sensory loss - Lateral aspect of thigh
Mononeuropathy Multiplex (-)
Definition
S/S
Mononeuropathy multiplex: simultaneous or sequential occurrence of mononeuropathies affecting multiple non-contiguous nerve trunks
Vasculitic Neuropathy leading to nerve infarction
□ Acute pain followed by focal neuropathy
□ Gradual spread from focal → multifocal → generalized
Causes of mononeuropathy multiplex (-)
□ Axonal due to nerve infarction from small-to-medium arterial diseases
→ DM-associated atherosclerosis
→ Vasculitis
→ Infections: syphilis, HIV, leprosy, Lyme disease, diphtheria
□ Demyelinating, eg. multifocal motor neuropathy (MMN)
Causes of mononeuritis multiplex:
Wegener’s granulomatosis
Amyloidosis
Rheumatoid arthritis
Diabetes mellitus
SLE
Polyarteritis nodosa
Leprosy
Carcinomatosis and Churg-strauss syndrome
4 clinical types of polyneuropathy
Typical S/S of polyneuropathy
Acute and Chronic axonal lesion
Acute and chronic demyelinating lesion
S/S: most typically symmetrical sensorimotor but other patterns possible
□ Motor: ascending weakness from distal LL
□ Sensory: ascending ‘glove-and-stocking’ sensory loss or paraesthesia from distal limbs
□ Autonomic: diarrhoea/constipation, brady/tachycardia, urinary disturbance, BP changes
GBS
- Pertinent features
- Pathophysiology
- Clinical course
- S/S
- First-line investigation
- Treatment
- Pertinent features: Rapidly progressive flaccid paralysis + areflexia + high CSF protein
- Pathophysiology: Recent VIRAL/ bacteria infection (e.g. COVID, URTI, GE) >>> acute neuritis from autoAb attack >> Acute inflammatory demyelinating polyneuropathy
- Clinical course: 4 weeks
- S/S: ascending weakness with facial involvement, LMN signs, Autonomic dysfunctions
- First-line investigation: Anti-Gangliocyte Antibody, High CSF without pleocytosis, Electrophysiology study
- Treatment: Plasmapheresis, IV immunoglobulins, Mechanical ventilation, Treat complications
Name the most commonly inherited neurological disorder
Charcot Marie Tooth Disease
Charcot Marie Tooth disease
- Features
- Mutation
Features: distal wasting, Foot drop, Pes cavus
Mutation: HMSN-I to HMSN-VII
Ddx motor neuron diseases
Pathophysiology
Treatment
ALS - Amyotrophic Lateral Sclerosis
PLS
Pseudobulbar palsy, PMA, PBP
Patho: Alpha motor neuron degeneration, No sensory involvement, Both UMN and LMN signs
Tx: None, general supportive only (ventialtion, euthansia, nutrition)
Ddx neurotoxic agents
Alcohol
Solvents
Industrical chemicals
Heavy metals
Anti-cancer agents, Anti-biotics
Colchine, Thalidomide…etc
Ddx Muscular dystrophies
3 ways to classify muscular dystrophies
- Dunchenne DMD
- Becker BMD
- Limb-girdle (LGMD)
- Myotonic dystrophy MyoD
- Fascioscapulohumeral FSHD
^^ Phenotype classification
- Immunohistochemical classification
- Genetic classification - e.g dystrophin gene deletion
Inflammatory myopathies ddx
Inclusion body myositis
Features
Investigations
Dermatomyositis
Features
Myositis investigations
Muscle MRI
PET scan for malignancy
Myositis - autoantibodies
ELISA
Electromyography
MG *
- Features
- Associated diseases
- First line IX
- Tx
Features: Fluctuating/ intermittent weakness, Anti-AchR antibodies, ocular manifestation first
Associated: Thymic Cancer, Autoimmune Thyroiditis
Ix: Anti-AchR Ab + Electrophysiology Tensilon test (injection Edrophonium) + CT thorax + Thyroid function test
Tx:
- Plasmapheresis, IV immunoglobulin
- Anti-cholinesterase (Pyridostigmine)
- Thymectomy
- Immunotherapy - Steroids, Azothioprine
Ddx Presynaptic NMJ disorder
Tests for clinical neurophysiology
Nerve conduction study
Needle electromyography (EMG)
Electrodiagnostic studies
