The problems of meningomyelocele and its complications are so largely pediatric and surgical that the neurologist seldom becomes involved—except perhaps in the initial evaluation of the patient—in the treatment of meningeal infection, or in the case of shunt failure with decompensation of hydrocephalus. Of greater interest to the neurologist are a series of closely related abnormalities that produce symptoms for the first time in late childhood, adolescence, or even adult life. These include sinus tracts with recurrent meningeal infections, lumbosacral lipomas with low tethering of the spinal cord (“tethered cord”) causing an early childhood or delayed radicular or spinal cord syndrome; diastematomyelia, cysts, or tumors with spina bifida and a progressive myeloradiculopathy; and the Chiari malformation and syringomyelia that first present in adolescence or adult life. These abnormalities are described below.
Another class of disorders involves an occult lumbosacral dysraphism that is not inherited but is a result of faulty development of the cell mass that lies caudal to the posterior neuropore (normally this undergoes closure by the 28th day of embryonic life). Occult spinal dysraphism of this type is also associated with meningoceles, lipomas, and sacrococcygeal teratomas. Another well-recognized anomaly is agenesis of the sacrum and sometimes the lower lumbar vertebrae (caudal regression syndrome). Interestingly, in 15 percent of such cases, the mother is diabetic (Lyon and Evrard). Here there is flaccid paralysis of legs, often with arthrogrypotic contractures and urinary incontinence. Sensory loss is less prominent, mental function develops normally, and there is no hydrocephalus.
Sinus tracts in the lumbosacral or occipital regions are of importance, for they may be a source of bacterial meningitis at any age. They are often betrayed by a small dimple in the skin or by a tuft of hair along the posterior surface of the body in the midline. (The pilonidal sinus should not be included in this group.) The sinus tract may lead to a terminal myelocystocele and be associated with dermoid cysts or fibrolipomas in the central part of the tract. Cloacal defects (no abdominal wall and no partition between bladder and rectum) may be combined with anterior meningoceles. Evidence of sinus tracts should be sought in instances of unexplained meningitis, especially when there has been recurrent infection or the cultured organism is of nosocomial dermal origin.
Of great interest are congenital cysts and tumors, particularly lipoma and dermoid, that arise in the filum terminale and attach (tether) the cord to the sacrum. Progressive symptoms and signs are produced as the spine elongates during development, thereby stretching the caudally fixed cord (Fig. 37-3). Some of these children have bladder and leg weakness soon after birth. Others deteriorate neurologically at a later age (generally between 2 and 16 years, sometimes later—see below). Complex disturbances of bladder function that produce urgency and incontinence beginning in the second or third decade may be the only manifestation, or the bladder symptoms may be combined with impotence (in the male) and numbness of the feet and legs or foot-drop (Pang and Wilberger). Several of our adult patients have had unusual visceral reflex reactions, such as involuntary defecation or priapism with stimulation of the abdomen or perineum. According to most surgeons, it is not the myelolipoma but the tethering of the cord that gives rise to symptoms; removal of the tumor is of little benefit unless the cord is detached from the sacrum at the same time. This may be difficult, for the lipoma may be fused with the dorsal surface of the spinal cord.