Mimics of Amyotrophic Lateral Sclerosis

DIAGNOSIS

In a patient with symptoms of footdrop or an atrophied hand, the diagnosis usually considered is an isolated lesion of a peripheral nerve or nerve root. If such a lesion is the initial sign of early motor neuron disease, careful testing of other muscles often reveals more diffuse motor weakness, typically in a myotomal pattern. Fasciculations and widespread evidence of atrophy on examination are useful additional diagnostic signs. Atrophy and fasciculations of the tongue may be the first sign of cranial nerve involvement. Reflexes may vary from depressed to brisk. The Babinski sign may be extensor or plantar, depending on whether lower or upper motor neuron involvement predominates. Sensory examination must be thorough and detailed, and results should be normal if motor neuron disease is present. The coexistence of both upper (increased tone, brisk reflexes) and lower motor neuron (atrophy, fasciculations) signs in the same limb is strongly suggestive of ALS.

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