Somatosensory evoked potential monitoring of peripheral nerves during external fixation for limb lengthening and correction of deformity in children.

We undertook a retrospective analysis of 306 procedures on 233 patients, with a mean age of 12 years (1 to 21), in order to evaluate the use of somatosensory evoked potential (SSEP) monitoring for the early detection of nerve compromise during external fixation procedures for limb lengthening and correction of deformity. Significant SSEP changes were identified during 58 procedures (19%). In 32 instances (10.5%) the changes were transient, and resolved once the surgical cause had been removed. The remaining 26 (8.5%) were analysed in two groups, depending on whether or not corrective action had been performed in response to critical changes in the SSEP recordings. In 16 cases in which no corrective action was taken, 13 (81.2%, 4.2% overall) developed a post-operative neurological deficit, six of which were permanent and seven temporary, persisting for five to 18 months. In the ten procedures in which corrective action was taken, four patients (40%, 1.3% overall) had a temporary (one to eight months) post-operative neuropathy and six had no deficit. After appropriate intervention in response to SSEP changes, the incidence and severity of neurological deficits were significantly reduced, with no cases of permanent neuropathy. SSEP monitoring showed 100% sensitivity and 91% specificity for the detection of nerve injury during external fixation. It is an excellent diagnostic technique for identifying nerve lesions when they are still highly reversible.

Felbamate urolithiasis.

PURPOSE: To report a case of felbamate (FBM) urolithiasis. METHODS: Urographic imaging [sonography, abdominal computed tomography (CT), intravenous pyelogram, voiding cystourethrogram] and urologic procedures (cystoscopy with lithotripsy, ureteral stent) to define and capture the stones. Stone identification was by infrared spectroscopy and gas chromatography/mass spectrometry. RESULTS: A 15-year-old boy had painful hematuria, bilateral ureteral obstruction, and urinary retention. Kidney, bladder, and ureteral stones were found, and ureteral stent placement was required to relieve obstruction. The stone material was identified as FBM by chemical analysis. Stone formation ceased with discontinuation of FBM. CONCLUSIONS: FBM urolithiasis can occur, and possible contributory factors include high felbamate dosage, drug polypharmacy, and risk factors for forming stones of other types. FBM urolithiasis may be heralded by crystalluria.

Tuberous sclerosis complex.

Tuberous sclerosis complex is an autosomal dominant disorder that causes significant complications in multiple organ systems. Both basic science and clinical research on tuberous sclerosis complex have flourished in recent years, improving our understanding of its molecular genetics and pathophysiology. Two tuberous sclerosis complex genes cause nearly identical phenotypes, and great progress has been made towards understanding how each of these genes functions. The recognition of tuberous sclerosis complex improved with revised diagnostic criteria, and the management of many of the complications of tuberous sclerosis complex has improved.

Abnormal sudomotor function in the hypomelanotic macules of tuberous sclerosis complex.

To investigate the integrity of sympathetic innervation in the hypomelanotic macules of tuberous sclerosis complex, we studied sudomotor function in nine patients with tuberous sclerosis complex. Postganglionic sudomotor function was assessed using the Silastic imprint test in nine patients with tuberous sclerosis complex who have at least one hypomelanotic macule greater than 2 cm in diameter. Sweating was induced by iontophoresis with 0.5% pilocarpine nitrate and sweat droplets were counted under a microscope using a 1 x 1 cm grid. Silastic imprint testing of an analogous skin area contralateral to the hypomelanotic macule was measured as a control. Sweat volume quantitation using sweat collectors was performed in five of the subjects. The sweat volume collected from the hypomelanotic macule was reduced compared to the control skin in four of the five subjects. Sweat droplet counts from the hypomelanotic macule were significantly reduced in only one of nine subjects. These data suggest that, although there is no difference in the number of functioning sweat glands in most hypomelanotic macules, the sweat glands produce less sweat (ie, decreased sweat volume) than in normal skin. We hypothesize that focal abnormalities of sympathetic innervation might be responsible for the hypomelanotic macules of tuberous sclerosis complex.

Dopa-responsive dystonia due to a large deletion in the GTP cyclohydrolase I gene.

Although it is assumed that most patients with autosomal dominant dopa-responsive dystonia (DRD) have a GTP cyclohydrolase I dysfunction, conventional genomic DNA sequencing of the gene (GCH1) coding for this enzyme fails to reveal any mutations in about 40% of DRD patients, which makes molecular genetic diagnosis difficult. We found a large heterozygous GCH1 deletion, which cannot be detected by the usual genomic DNA sequence analysis, in a three-generation DRD family and conclude that a large genomic deletion in GCH1 may account for some "mutation-negative" patients with dominantly inherited DRD.

Renal lesion growth in children with tuberous sclerosis complex.

PURPOSE: Renal lesions, including angiomyolipoma, renal cysts (simple and polycystic kidney disease) and renal cell carcinoma, develop in patients with tuberous sclerosis complex. While there is limited information that these lesions may grow in adults with tuberous sclerosis complex, the incidence, characterization and growth rate in children have not been reported. Also, the age at which these lesions first appear, thus providing insight into their natural history, is unknown. We present our data from a longitudinal renal surveillance study of children with tuberous sclerosis complex. MATERIALS AND METHODS: Since 1985 children with tuberous sclerosis complex at our hospital have undergone periodic renal imaging by ultrasonography or computerized tomography to monitor renal lesions. A total of 35 girls and 25 boys 1 to 18 years old have undergone at least 2 or more annual renal ultrasounds. RESULTS: On initial evaluation 33 of 60 children (55%) (mean age 6.9 years) had an identifiable renal lesion, which increased to 48 of 60 (80%) at followup (mean age 10.5 years). Angiomyolipoma was the most frequent lesion (75%) followed by simple renal cysts (17%). Angiomyolipomas increased in size and/or number in 10 of 18 boys (56%) and 18 of 27 girls (66%). The largest growth rate in 1 year was from 0 to 4 cm. and from 5 to 9 cm. in diameter. The youngest patient demonstrated lesions at age 2 years. The average age at which a normal ultrasound became abnormal was 7.2 years. While a total of 27 patients had a normal ultrasound on entering the study, lesions had developed in 15 at followup (11 with angiomyolipomas, 4 with cysts). Five patients had cysts that had disappeared at followup. A 7-year-old boy had a 9 cm. renal cell carcinoma removed. One patient has renal lesions characteristic of autosomal dominant polycystic kidney disease. CONCLUSIONS: Renal involvement in patients with tuberous sclerosis complex begins in infancy, and angiomyolipoma is the most common lesion (75%). Angiomyolipomas are more likely to grow than remain stable, although the rate of growth varies. Simple renal cysts may appear or disappear with time but angiomyolipomas do not disappear. An initially normal renal ultrasound does not rule out future development of lesions. Periodic surveillance is indicated in children with tuberous sclerosis complex.

Early diagnosis of subependymal giant cell astrocytoma in patients with tuberous sclerosis.

We present 19 patients with tuberous sclerosis complex and subependymal giant cell astrocytoma. The mean age at the time of tumor diagnosis was 9.4 years (range, 1.5 to 21 years). Computed cranial tomography (CT) or cranial magnetic resonance imaging (MRI) identified the lesion which was resected in all cases. Seven patients had hydrocephalus and there was an interval increase in the tumor size or a large tumor without hydrocephalus in 12 patients. Surgical criteria included: (1) presence of hydrocephalus; (2) interval increase in tumor size; (3) new focal neurologic deficit attributable to the tumor; and/or (4) symptoms of increased intracranial pressure. Eight patients were identified through a surveillance program involving annual computed cranial tomography. All of these eight patients had their tumor removed prior to the development of symptoms, none had neurologic deficits which persisted after surgery, and none has so far developed recurrent subependymal giant cell astrocytoma. In contrast, of the 11 patients from the non-surveillance group 7 were symptomatic at tumor diagnosis, 1 had a complicated postoperative course, 2 developed recurrent giant cell astrocytoma, and 1 had an extensive lesion that could not be completely excised. Periodic cranial imaging may help to identify subependymal giant cell astrocytomas in tuberous sclerosis patients before they become symptomatic. Earlier diagnosis and treatment could reduce surgical morbidity and the risk of tumor recurrence.