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Key Features

Essentials of Diagnosis

  • Weakness and wasting of muscles

  • No sensory loss or sphincter disturbance

  • Progressive course

  • No identifiable underlying cause other than genetic basis in familial cases

  • Cigarette smoking may be a risk factor

General Considerations

  • There is degeneration of the

    • Anterior horn cells in the spinal cord

    • Motor nuclei of the lower cranial nerves

    • Corticospinal and corticobulbar pathways

  • Five varieties have been characterized on clinical grounds

PROGRESSIVE BULBAR PALSY

  • Bulbar involvement predominates

  • Disease processes affect primarily the motor nuclei of the cranial nerves

PSEUDOBULBAR PALSY

  • Bulbar involvement predominates

  • Due to bilateral corticobulbar disease and thus reflects upper motor neuron dysfunction

PROGRESSIVE SPINAL MUSCULAR ATROPHY

  • A lower motor neuron deficit in the limbs

  • Due to degeneration of the anterior horn cells in the spinal cord

PRIMARY LATERAL SCLEROSIS

  • There is a purely upper motor neuron deficit in the limbs

AMYOTROPHIC LATERAL SCLEROSIS

  • A mixed upper and lower motor neuron deficit is found in the limbs

  • Approximately 10% of cases of amyotrophic lateral sclerosis are familial

  • This disorder is sometimes associated with cognitive decline (in a pattern consistent with frontotemporal dementia), a pseudobulbar affect, or parkinsonism

Demographics

  • Symptoms generally begin between 30 and 60 years of age

  • The disease is usually sporadic, but familial cases may occur

Clinical Findings

Symptoms and Signs

  • Difficulty in swallowing, chewing, coughing, breathing, and talking (dysarthria) occur with bulbar involvement

  • In progressive bulbar palsy, there is

    • Drooping of the palate

    • A depressed gag reflex

    • Pooling of saliva in the pharynx

    • A weak cough

    • A wasted, fasciculating tongue

  • In pseudobulbar palsy, the tongue is contracted and spastic and cannot be moved rapidly from side to side

  • Limb involvement is characterized by motor disturbances (weakness, stiffness, wasting, fasciculations) reflecting lower or upper motor neuron dysfunction

  • There are no objective changes on sensory examination, though there may be vague sensory complaints

  • The sphincters are generally spared

Differential Diagnosis

UPPER MOTOR NEURON DISEASE

  • Stroke

  • Space-occupying lesion

  • Compressive spinal cord lesion

  • Multiple sclerosis

LOWER MOTOR NEURON DISEASE

  • Infections of anterior horn cells (eg, poliovirus or West Nile virus)

  • Radiculopathy, plexopathy, peripheral neuropathy, and myopathy are distinguished by clinical examination

  • Pure motor syndromes resembling motor neuron disease may occur in association with

    • Monoclonal gammopathy

    • Multifocal motor neuropathies with conduction block, which can be distinguished by electrodiagnostic studies

  • A motor neuronopathy may develop in Hodgkin disease and has a relatively benign prognosis

Diagnosis

Laboratory Tests

  • The serum creatine kinase ...

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