THE CASE
A 39-year-old man who worked in construction presented to our clinic with complaints of muscle cramps and muscle pain that had been bothering him for several months. The cramps and pain started in both of his arms and subsequently became diffuse and generalized. He also reported an unintentional 15-pound weight loss.
His exam at that time was unremarkable. He was diagnosed with dehydration and cramping due to overexertion at work. A basic metabolic panel, hemogram, lipid panel, and thyroid stimulating hormone level were ordered. The patient’s triglyceride level, which was 227 mg/dL, was the only significant result (normal level: <150 mg/dL).
The patient’s symptoms continued to worsen until he returned to the clinic 6 months later, again complaining of muscle cramps and pain throughout his body. At that second visit, he also reported profound overall weakness and the development of diffuse muscle twitching, which his wife had observed while he was sleeping. As a result of these worrisome symptoms, he had become anxious and depressed.
A review of his medical record revealed a weight loss of about 20 pounds over the previous year. On exam, he had diffuse fasciculations in all the major muscle groups, including his tongue. The patient’s strength was 4/5 in all muscle groups. His deep tendon reflexes were 3+. He had a negative Babinski reflex (ie, he had downward facing toes with plantar stimulation), and cranial nerves II to XII were all intact. His rapid alternating movements and gait were slow.
THE DIAGNOSIS
Based on the exam, the primary diagnostic consideration for the patient was amyotrophic lateral sclerosis (ALS). Lab tests were ordered and revealed normal calcium and electrolyte levels, a normal erythrocyte sedimentation rate, a normal C-reactive protein level, and a negative test for acetylcholine receptor antibodies. However, the patient had an elevated creatine kinase level of 664 U/L (normal: 30-200 U/L). The patient was sent to a neuromuscular specialist, who identified signs of upper and lower motor neuron disease in all 4 of the patient’s extremities (he had foot drop that had not been present previously) and a very brisk jaw jerk. Along with the tongue fasciculations, the results of the specialist’s physical exam suggested ALS. Four-limb electromyography (EMG) showed widespread fasciculations and some large motor unit potentials and recruitment abnormalities, which were also consistent with ALS. It appeared that the patient’s weight loss was due to both muscle atrophy and the amount of calories burned from his constant twitching.
Extensive testing was done to rule out other potential causes of the patient’s symptoms, including magnetic resonance imaging (MRI) of the spine and brain (which was normal). In addition, the patient’s aldolase level and antineutrophil cytoplasmic antibodies were normal. The patient tested negative for human immunodeficiency virus and antibodies to double-stranded DNA. After serial neurologic exams, the final diagnosis of ALS was made.
DISCUSSION
ALS, also known as Lou Gehrig’s disease, is a degenerative motor neuron disease.1-3 The incidence in North America is 1.5 to 2.7 per 100,000 per year, and the prevalence is 2.7 to 7.4 per 100,000.4 The incidence of ALS increases with each decade of life, especially after age 40, and peaks at 74 years of age.4 The male to female ratio is 1:1.5-2.4 ALS affects upper and lower motor neurons and is progressive; however, the rate of progression and phenotype vary greatly between individuals.2 Most patients with ALS die within 2 to 5 years of onset.5
There is no specific test for ALS; the diagnosis is made clinically based on the revised El Escorial World Federation of Neurology criteria, also known as the Airlie House criteria.2,6,7 These criteria include evidence of lower motor neuron degeneration by clinical, electrophysiologic, or neuropathologic exam; evidence of upper motor neuron disease by clinical exam; progressive spread of symptoms or signs within a region or to other regions (by history or exam); and the absence of electrophysiologic, neuroimaging, or pathologic evidence of other disease processes that could explain the symptoms. If patients have evidence of upper and lower motor neuron disease, they should be reevaluated in 4 weeks to see if symptoms are improving or progressing.
Like our patient, many patients will have an elevated creatine kinase level (some with levels as high as 1000 U/L), and calcium may also be elevated because, rarely, ALS is associated with primary hyperparathyroidism.8 Electrophysiologic studies can be helpful in identifying active denervation of lower motor neurons.4,6,7