A 62-year-old Caucasian man comes to the physician because of progressive weight loss and right lower extremity weakness for the last two months. On further questioning, he tells you that he has been having frequent leg cramps in the right leg. These cramps are most prominent in the morning, after he wakes up. He also has difficulty with swallowing and chewing. He denies any problems with bowel or bladder function. His other medical problems include hypertension and hypercholesterolemia. He does not use tobacco. His family history is not significant. His vital signs are within normal limits. The physical examination reveals weakness in his right lower leg, atrophy and fasciculation of the thigh and calf muscles, a hyperactive knee jerk, and tongue fasciculations. The rest of his neurological examination, including the sensory examination, is normal. Item 1 of 2
Which of the following is the most likely diagnosis?

Question

Quizplus · Accepted Answer

Explanation: Amyotrophic lateral sclerosis (ALS) is the most common form of progressive motor neuron disease. It is a relentlessly progressive disorder that involves both the lower motor neurons (consisting of anterior horn cells in the spinal cord and brainstem neurons innervating the bulbar muscles) and upper or corticospinal motor neurons. At its onset, ALS may involve selective loss of function of only upper or lower motor neurons, but it ultimately causes progressive loss of both upper and lower motor neurons. The initial sign of the disease with lower motor neuron involvement is an insidiously developing asymmetric weakness, usually first evident distally in one of the limbs. Patients may disclose a history of recent development of cramping with volitional movements that typically occur in the early morning hours (e.g. while stretching in bed). Weakness is associated with progressive wasting, atrophy of muscles, and spontaneous twitching or fasciculations of motor units. Involvement of the bulbar muscles leads to difficulty with chewing and swallowing, as well as fasciculations of the face and tongue. ALS with prominent corticospinal involvement is characterized by hyperactivity of muscle-stretch reflexes (tendon jerks) and frequent spastic resistance to passive movements of the affected limbs. Ocular motility, sensory, bowel, bladder, and cognitive functions are preserved, even with advanced disease. (Choice B) Vascular dementia is characterized by the presence of behavioral disturbances and cognitive deficits associated with clinical or radiographic evidence of a stroke. The decline in the level of cognition is relatively abrupt and progresses in a stepwise fashion. (Choice A) Binswanger's disease is a type of vascular dementia that involves white matter infarcts. Patients with this disease usually present with apathy, agitation, and bilateral corticospinal or bulbar signs. (Choice C) Multiple sclerosis is usually seen in younger females with two or more clinically distinct episodes of CNS dysfunction. Patients typically have sensory, visual, or bladder and bowel dysfunction. (Choice E) Brain stem tumors may compress the cervical cord and produce weakness, fasciculations in the upper limbs, and spasticity in the legs. The presentation may closely resemble ALS; however, absence of pain or sensory changes and normal bowel and bladder function in the patient favor ALS. Educational Objective: ALS should be suspected in patients who present with progressive weakness accompanied by both upper and lower motor neuron deficits. Ocular motility, sensory, bowel, bladder, and cognitive functions are preserved, even with advanced disease.

A 62-Year-Old Caucasian Man Comes to the Physician Because of Progressive