Neurology Case Challenge: A Man With Buttocks Pain, Bladder and Bowel Incontinence

Xuan Kang, MD


July 21, 2022

Physical Examination and Workup

Upon physical examination, the patient appears cachectic. His blood pressure is 93/57 mm Hg, heart rate is 79 beats/min, respiration rate is 16 breaths/min, oxygen saturation is 95% on room air, and temperature is 97°F (36.1°C). He is 5 ft 9 in (1.75 m) tall and weighs 125 lb (56.7 kg). His body mass index is 18 kg/m2.

The cranial nerve and upper-extremity examination results are normal. The lower-extremity examination reveals purplish skin discoloration below the upper thigh, which is extremely cold to touch, with prominent muscle atrophy and flexion contractures at both knees. He has 2/5 hip abduction bilaterally, restricted bilateral knee extension, and 4/5 strength with knee flexion. Ankle movements are absent on the left and are of 2/5 strength on the right; toe movements and reflexes in the lower extremities are absent. Proprioception, vibratory sensation, and temperature sensation are absent below the hip.

The results of a serum laboratory workup — including hepatitis C polymerase chain reaction, human T-cell lymphotropic virus, antimyelin oligodendrocyte glycoprotein, neuromyelitis optica immunoglobulin G, cryoglobulin, rheumatoid factor, antinuclear antibody with reflex panel, HIV, antineutrophil cytoplasmic antibody, vitamin B12, vitamin B6, and angiotensin-converting enzyme tests —are normal. A lumbar puncture is performed, and cerebrospinal fluid (CSF) analysis reveals 3 nucleated cells/µL, 2 red blood cells cells/µL, a protein level of 45 mg/dL (reference range, 15-45 mg/dL), and no oligoclonal bands, with negative cytology. The erythrocyte sedimentation rate is 31 mm/hr (reference range, 0-15 mm/hr), and the C-reactive protein level is 113 mg/L (reference range, < 10.0 mg/L). The results of additional serum and CSF studies are pending. A brain MRI scan with and without contrast is normal.

A subsequent electrophysiologic study demonstrates near-absent sensory and motor responses in the bilateral lower extremities, with severe active and chronic neurogenic changes in all proximal and distal muscles tested, including the paraspinal muscles. The upper extremity study is normal. No conduction block or temporal dispersion is visualized on the electrodiagnostic study.

MRI of the cervical and thoracic spine is normal. MRI of the lumbar spine demonstrates contrast enhancement in the cauda equina nerve roots, without a compressive cause (Figure 1). MRI of the lumbar plexus shows contrast enhancement and muscular edema involving the proximal lower-extremity muscles.

Figure 1.


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