A Man With Progressive Leg Muscle Weakness 20 Years After an Acute Paralysis

A 54-year-old man presented initially at age 24 with an acute episode of right lower extremity weakness and urinary hesitancy. Examination at that time revealed right lower extremity weakness of 3/5 proximally and distally, decreased sensation over both feet, ankles, and right saddle area, absent right lower extremity reflexes, and diminished left ankle jerk. Atrophy was not documented. Cerebrospinal fluid was normal with protein 26 mg/dL (normal, 20–w40 mg/dL), glucose 77 mg/dL (normal, 40–60 mg/dL), 1 white cell/mm ³ (normal, 0–5 white cell/mm ³ ), and normal protein electrophoresis.

Electrodiagnostic studies were not performed at that time, and MRI was not availablew. He improved over 18 months but continued to have residual perianal and right foot numbness; he also required self-catheterization for 4 years followed by occasional bladder evacuation difficulties for years. Eight years after the initial episode, he developed “chronic fatigue syndrome” with a positive Epstein–Barr virus antibody, which resolved with acyclovir therapy.

Although he had mild residual right foot weakness, he remained physically active and played tennis several times a week until age 42, when he presented with progressive right lower extremity wasting and weakness. He denied back or leg pain or sexual dysfunction. The bladder symptoms had resolved.

Examination at the time revealed weakness and wasting of the right tibialis anterior (3/5), gastrocnemius, tibialis posterior and peronei (4/5). Upper and lower extremity reflexes were normal. Pinprick sensation was diminished over the left foot and perianal region. Plantar responses were flexor. Rectal tone was normal. Over the next 2 years, he developed weakness of the right quadriceps and hamstrings (4/5), ankle areflexia, and right knee hyporeflexia. The right leg was 4.5 cm smaller in circumference at mid-calf ( Fig. 34-1 ).

The weakness increased over the next 6 years. Playing tennis became difficult as he tended to trip over his right foot. Limb measurements revealed a 1-cm decrease in right calf girth over 6 years. During 1 year prior to the present evaluation, he noted difficulty in standing on his left toes.

The following studies were unremarkable: blood counts, chemistries, creatine kinase, thyroid functions, vitamin B ₁₂ , folate, rheumatoid factor, serum protein electrophoresis and immunoelectrophoresis, ganglioside antibodies, antibodies to myelin-associated glycoprotein, Lyme antibodies, and cytomegalovirus antibodies. Cerebrospinal fluid examination was normal, with protein 28 mg/dL, glucose 69 mg/dL, and no cells. The IgG index was 0.4 (normal, 0.3–0.7) and myelin basic protein 0.7 ng/mL (normal, <0.5 ng/mL). The fluorescent antinuclear antibody test was weakly positive at 1:80. Epstein–Barr virus antibody (IgG) was positive. Poliovirus antibody titers were not measured.

What is the Differential Diagnosis and What Tests need to be Done?

The progressive nature of the condition suggests a motor neuron disease, but the sensory changes and urinary symptoms are against this diagnosis. The slow progression and focal presentation make a mononeuritis multiplex unlikely, but a plexopathy is possible. Spinal canal diseases, such as a tumor and stenosis, or syringomyelia, are also considerations, and because the symptoms have always been localized to the spinal cord territory, a localized benign lesion such as a hemangioma or arteriovenous malformation with focal edema remains a possibility. Benign focal amyotrophy usually affects the upper extremities but can occur in the legs. This disorder, however, is not progressive.

An EMG could document the characteristics and distribution of the pathology and determine if there is a radiculopathy, a plexopathy, or a recent diffuse motor neuron disease.