Hindsight Is 20/20

A 38-year-old woman presented to her primary care clinic with 3 weeks of progressive numbness and tingling sensation, which began in both hands and then progressed to involve both feet, ascending from the legs to the chest while sparing her buttocks. She also noted weakness of her left leg, but no other motor symptoms were reported. She had no fevers, chills, weight loss, bladder dysfunction, nausea, vomiting, or diarrhea.

As with all neurological complaints, localization of the process will often inform a more specific differential diagnosis. If both sensory and motor findings are present, both central and peripheral nerve processes deserve consideration. The onset of paresthesia in the hands, rapid progression to the trunk, and unilateral leg weakness would be inconsistent with a length-dependent peripheral neuropathy. The distribution of complaints and the sacral sparing suggests a myelopathic process involving the cervical region rather than a cauda equina or conus lesions. In an otherwise healthy person of this age and gender, an inflammatory demyelinating disease affecting the cord including multiple sclerosis (MS) would be a strong consideration, although metabolic, vascular, infectious, compressive, or neoplastic disease of the spinal cord could also present with similar subacute onset and pattern of deficits.

Her medical history included morbid obesity, dry eyes, depression, iron deficiency anemia requiring recurrent intravenous replenishment, and abnormal uterine bleeding. Her surgical history included gastric band placement 7 years earlier with removal 5 years later due to persistent gastroesophageal reflux disease, dysphagia, nausea, and vomiting. The gastric band removal was complicated by chronic abdominal pain. Her medications consisted of duloxetine, intermittent iron infusions, artificial tears, loratadine, and pregabalin. She was sexually active with her husband. She consumed alcohol occasionally but did not smoke tobacco or use illicit drugs.

On exam, her temperature was 36.6°C (97.8°F), blood pressure 132/84 mm Hg, and heart rate 85 beats per minute. Body mass index was 39.5 kg/m². The cardiac, pulmonary, and skin examinations were normal. The abdomen was soft with diffuse tenderness to palpation without rebound or guarding. Examination of cranial nerves 2-12 was normal. Cognition, strength, proprioception, deep tendon reflexes, and light touch were all normal. Her gait was normal, and the Romberg test was negative.

The normal neurologic exam is reassuring but imperfectly sensitive and does not eliminate the possibility of underlying neuropathology. Bariatric surgery may result in an array of nutritional deficiencies such as vitamin E, B12, and copper, which can cause myelopathy and/or neuropathy. However, these abnormalities occur less frequently with gastric banding procedures. If her dry eyes are part of the sicca syndrome, an underlying autoimmune diathesis may be present. Her unexplained chronic abdominal pain prompts considering nonmenstrual causes of iron deficiency anemia, such as celiac disease. Bariatric surgery may contribute to iron deficiency through impaired iron absorption. Her stable weight and lack of diarrhea argue against Crohn’s or celiac disease. Iron deficiency predisposes individuals to pica, most commonly described with ice chip ingestion. If lead pica had occurred, abdominal and neurological symptoms could result. Nevertheless, the abdominal pain is nonspecific, and its occurrence after gastric band removal makes its link to her neurologic syndrome unclear. An initial evaluation would include basic metabolic panel, complete blood count with differential, erythrocyte sedimentation rate, C-reactive protein (CRP), thyroid-stimulating hormone, vitamin B12, and copper levels.

A basic metabolic panel was normal. The white cell count was 5,710 per cubic millimeter, hemoglobin level 12.2 g per deciliter, mean corpuscular volume 85.2 fl, and platelet count 279,000 per cubic millimeter. The serum ferritin level was 18 ng per milliliter (normal range, 13-150), iron 28 µg per deciliter (normal range, 50-170), total iron-binding capacity 364 µg per deciliter (normal range, 250-450), and iron saturation 8% (normal range, 20-55). The vitamin B12 level was 621 pg per milliliter (normal range, 232-1,245) and thyroid-stimulating hormone level 1.87 units per milliliter (normal range, 0.50-4.50). Electrolyte and aminotransferase levels were within normal limits. CRP was 1.0 mg per deciliter (normal range, <0.5) and erythrocyte sedimentation rate 33 millimeters per hour (normal range, 4-25). Hepatitis C and HIV antibodies were nonreactive.

The ongoing iron deficiency despite parenteral iron replacement raises the question of ongoing gastrointestinal or genitourinary blood loss. While the level of vitamin B12 in the serum may be misleadingly normal with cobalamin deficiency, a methylmalonic acid level is indicated to evaluate whether tissue stores are depleted. Copper levels are warranted given the prior bariatric surgery. The mild elevations of inflammatory markers are nonspecific but reduce the likelihood of a highly inflammatory process to account for the neurological and abdominal symptoms. 

At her 3-month follow-up visit, she noted that the paresthesia had improved and was now limited to her bilateral lower extremities. During the same clinic visit, she experienced a 45-minute episode of ascending left upper extremity numbness. Her physical examination revealed normal strength and reflexes. She had diminished response to pinprick in both legs to the knees and in both hands to the wrists. Vibration sense was diminished in the bilateral lower extremities.