Literature

Clinical Pearls & Morning Reports


By Carla Rothaus

Published November 15, 2017

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Zinc-induced copper deficiency appears to result from the competitive relationship between zinc absorption and copper absorption in enterocytes, which is mediated by the protein metallothionein. Read the latest Case of the Massachusetts General Hospital.

Clinical Pearls

Q: What are some of the features of the myelopathy associated with a spinal dural arteriovenous fistula?

A: A spinal dural arteriovenous fistula is a direct communication between a spinal artery and a spinal vein without an intervening capillary bed, and it leads to venous congestion, edema, and ischemia of the cord parenchyma. Patients with a spinal dural arteriovenous fistula classically present with nonspecific spinal-cord dysfunction, chronic and progressive sensory loss, weakness, and incontinence, typically beginning in the fifth or sixth decade of life. In 80% of reported cases of spinal dural arteriovenous fistulas, the myelopathy affects the thoracolumbar segments between T6 and L2. Cervical involvement is rare.

Q: What nutritional deficiencies may occur in patients who have undergone Roux-en-Y gastric bypass?

A: Roux-en-Y gastric bypass procedure results in the creation of a small proximal stomach pouch directly connected to the midjejunum, thus bypassing most of the stomach, duodenum, and proximal jejunum — the portion of the digestive tract that is critical for fat and mineral absorption. The procedure produces a malabsorptive state that can result in numerous nutritional deficiencies, including deficiencies in vitamins A, B1, B2, B6, B9, B12, D, and E, as well as iron, copper, and other micronutrients. After surgery, patients who have intractable vomiting, cannot tolerate food, use alcohol excessively, lose more weight than expected, or do not take vitamin supplementation as instructed are at the greatest risk for the development of nutritional deficiencies.

Morning Report Questions

Q: How often do neurologic complications occur as a complication of bariatric surgery?

A: Neurologic disorders occur as a complication of bariatric surgery in 5 to 16% of patients and are largely attributed to nutritional deficiencies. Such disorders are classified according to the time of onset. Myelopathy is considered to be a late complication; it typically occurs an average of 9 years after bariatric surgery. Nutritional deficiencies that are specifically associated with myelopathy include deficiencies in vitamins B9, B12, and E and copper. Reports of myelopathy due to vitamin E deficiency after bariatric surgery are rare; when such a condition is reported, it is often seen in combination with more common nutritional deficiencies, including vitamin B12 or copper deficiency.

Q: What are some of the causes and manifestations of copper deficiency?

A: Copper deficiency occurs in a variety of disorders (e.g., celiac disease) and hereditary conditions (e.g., Menkes disease). Copper is predominantly absorbed in the duodenum, and thus copper deficiency is a known complication of Roux-en-Y gastric bypass. An increased blood zinc level is associated with copper deficiency. Zinc toxicity occurs as a result of excess zinc in the diet or in dietary supplements or as a result of the use of dental adhesives that contain zinc. Neurologic manifestations of copper deficiency include myelopathy, polyneuropathy, optic neuropathy, myopathy, and motor neuron disease. Copper deficiency has also been associated with hematologic abnormalities, including anemia (typically normocytic, macrocytic, or sideroblastic), neutropenia, and in rare cases, thrombocytopenia. On laboratory testing, the hallmark of copper deficiency is a low blood copper level; 45% of patients have a level lower than 0.10 μg per milliliter (1.57 μmol per liter).

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