Upper Motor Neuron
Etiology
- Hemiplegia/Quadriplegia
- Extrapyramidal Disorders
- Multiple Sclerosis
- Spinal Cord Injuries
Clinical Features
- Weakness
- Hyperreflexia
- Increased muscle tone
- Sensory/autonomic changes (variable)
Diagnosis
Lower Motor Neuron
Etiology
- Paralytic Polio/Post-Polio Syndrome
- ALS
- Werdig-Hoffman Disease
- Spinal Muscular Atrophies
Clinical Features
- Weakness
- Hyperreflexia
- Atrophy
- Flaccidity
- Fasciculations
- Bulbar involvement
- Absence of sensory changes
Diagnosis
- EMG: dennervation potentials, giant motor units
- NCV: normal
Peripheral Nerve
Etiology
- Guillain-Barre Syndrome: ascending paralysis (similar to tick paralysis, in contrast to descending paralysis seen in paralytic-neurotoxic shellfish poisoning and botulism)
- Chronic Inflammatory Demyelinating Polyneuropathy
- Acute Intermittent Porphyria
- Toxic Polyneuropathies (lead/thallium/triorthocresyl phosphate/saxitoxin/alcoholic)
- Other Polyneuropathies: SLE/PAN/diabetic/critical illness/diphtheria/Lyme disease
- Paralytic-Neurotoxic Shellfish Poisoning: descending paralysis (in contrast to ascending paralysis seen in GBS and tick paralysis)
Clinical Features
- Weakness
- Hyporeflexia
- Flaccidity
- Bulbar involvement
- Sensory/ autonomic changes
Diagnosis
- EMG: dennervation potentials (in axonal neuropathies)
- NCV: decreased
Neuromuscular Junction
Etiology
- Myasthenia Gravis
- Botulism: descending paralysis (in contrast to ascending paralysis seen in GBS and tick paralysis)
- Lambert-Eaton Myasthenic Syndrome (LEMS)
- Organophosphate Intoxication
- Tick Paralysis: ascending paralysis (similar to GBS, in contrast to descending paralysis seen in paralytic-neurotoxic shellfish poisoning and botulism)
Clinical Features
- Fluctuating weakness
- Fatigability
- Ocular and bulbar involvement
- Normal reflexes
- Absence of sensory changes
Diagnosis
- EMG: changes in amplitude of muscle response to repetitive stimulation
- NCV: normal
Muscle
Etiology
- Critical Illness Polymoypathy
- Muscular Dystrophies
- Polymyositis
- Acid Maltase Deficiency
- Carnitine Palmityl Transferase Deficiency
Clinical Features
- Typically proximal weakness
- Normal reflexes
- Absence of sensory/autonomic changes
- Myalgia (often present)
Diagnosis
- EMG: small motor units
- NCV: normal