The angulation of the sacrum is easily measured. The authors have previously reported on patients who were symptomatic with a diagnosis of myelomeningocele who were found to have changes in their lumbosacral angle (LSA) corresponding to the onset of symptoms indicative of a tethered spinal cord. The aim of this study was to verify this same finding in a group of patients with occult spinal dysraphism (that is, closed neural tube defect).
A retrospective analysis of 50 consecutive lipomyelomeningocele repair procedures was performed. Data pertaining to 30 age-matched control patients were also analyzed. Measurements were made of the LSA over time in all studied patients harboring lipomyelomeningoceles.
Appropriate imaging was available for 25 cases of lipomyelomeningocele (that is, radiographs of the lumbosacral junction were available from the patient’s perinatal period and at presentation of symptoms of a tethered spinal cord). Roughly one third of these patients suffered symptoms from a tethered spinal cord at the most recent follow-up examination. Nine patients (36%) were found to have corresponding LSA measurements greater than 70°, and seven (28%) of these patients presented with signs and symptoms of a tethered spinal cord, such as decreased lower-extremity function (two patients), urinary bladder incontinence (three patients), back pain (one patient), and lower-extremity paresthesias (one patient). The LSA measurements were statistically greater (p < 0.05) in the symptomatic patient population than in age-matched control patients and asymptomatic patients. Changes in the LSA in these symptomatic patients ranged from 5 to 24° (mean 13°). Changes in the LSA were noted in only two asymptomatic patients. No single sign or symptom of a tethered spinal cord appeared to correlate to any degree of increase in the LSA. Of the 25 patients excluded from this study because perinatal radiographic images were not available, none was symptomatic at the most recent follow-up examination and none had a grossly exaggerated LSA.
Signs and symptoms indicative of a tethered spinal cord appear to correspond to increases in the LSA. Although the authors do not advocate the use of LSA measurement as the sole indicator of a tethered spinal cord, this imaging finding may prove useful to the clinician as an indication of the tethered spinal cord or as an adjunct in verifying symptomatology in patients harboring a lipomyelomeningocele.