Neuro Localization

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

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