Nephrogenic Diabetes Insipidus and Tethered Cord Syndrome with a Lipoma of the Cauda Equina

Title: Nephrogenic Diabetes Insipidus and Tethered Cord Syndrome with a Lipoma of the Cauda Equina
Authors: Fujii, Tatsuya; Ochi, Junko; Miyajima, Tomoko; Yorifuji, Tohru; Ueda, Tomohiro; Koyama, Tsunemaro; Ito, MD, Masafumi
Publisher: Brain & Development
Date Published: 1998
Reference Number: 155
The tethered cord syndrome is characterized by sensory and motor disturbances of the lower extremities and incontinence. We report a 12-year-old girl with a cauda equina lipoma and a tethered spinal cord, whose chief complaints were polyuria and polydipsia. She was diagnosed as having nephrogenic diabetes insipidus. This unusual complication of the tethered cord syndrome was most likely due to a hydronephrosis secondary to a neurogenic bladder. Thus, spinal lesions have to be considered in patients with polyuria and polydipsia.

This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)

Tethered cord syndrome is a congenital disorder resulting from defective closure of the neural tube in the spine. The cone-shaped lower end of the spinal cord called the conus medullaris is abnormally low and is restricted by any one of a number of fibers within the outer membranes covering the spinal cord. A person with tethered cord syndrome may be afflicted with sensory and motor disturbances of the lower extremities and incontinence. Fujii, et al., report on a 12-year-old girl with a tethered spinal cord and a condition called cauda equina lipoma, which occurs when a collection of spinal roots descends from the lower part of the spinal cord and occupies the vertebral canal below the cord. The resultant tangle looks like a horse's tail.

The girl's main complaints were polydipsia (chronic, excessive thirst) and polyuria (chronic, excessive urination). She was born with a dimple in her left sacral area (which can indicate an abnormality), but had no apparent symptoms until she was about one and a half when she developed a slight limp which disappeared after a while. She had wet her bed every night since infancy, but never complained of or evidenced incontinence during the day.

Testing indicated diabetes insipidus. When she did not respond to infusions of synthetic arginine vasopressin, she was diagnosed with partial nephrogenic diabetes insipidus (NDI). She had a distended bladder, distention of the pelvic areas and calices (cup-shaped areas) of her kidney, a dimple in her sacral area, and a deviated sacrum. She also had a benign tumor in her cauda equina. She also had a low-set spinal cord and thickened connective tissue in the lower area of her spine. She was operated on to correct the tethering of her spinal cord, which restored her left Achilles tendon reflex. However, her bladder control did not improve significantly and the distention of her kidney pelvises and calices was only relieved through intermittent urethral self-catheterization.

Despite frequent involvement of the bladder in tethered cord syndrome, nephrogenic diabetes insipidus has never before been reported in patients having this syndrome (or having a tumor in their cauda equina). Perhaps this extreme rare case occurred because it takes a long time for nephrogenic diabetes to develop as a result of the damage tethered cord syndrome can cause to the kidney, and most people with tethered cord syndrome are diagnosed and treated long before NDI has a chance to develop. (This patient remained undiagnosed for more than ten years.) This case report shows the importance of careful neurological and urological examination of patients with persistent urination during the night or a dorsal dermal dimple, even without apparent symptoms. This case also shows that the tethered cord syndrome or an intraspinal lipoma (benign tumor in the spine) may cause NDI.