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

• EMG: normal
• NCV: normal

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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

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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

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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

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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