INTRODUCTION

Cutaneous neural heterotopias comprise a diverse group of lesions, including tumors and malformations, in which leptomeningeal or glial tissue is present in the dermis and subcutaneous tissue. Heterotopic neural malformations of the scalp are congenital and result from aberrant neural tube closure. They have no malignant potential. These anomalies are seen in newborns as a nodule in the occipital or parietal scalp with overlying alopecia. Often there is an associated capillary stain and a surrounding circle of long, course hair, a finding termed the "hair collar sign". While most of these lesions are separated from the underlying central nervous system by intact calvaria, some have a rudimentary stalk that communicates intracranially.

MATERIALS AND METHODS

We retrospectively reviewed the records of 10 infants with heterotopic neural malformations of the scalp managed at Children's Hospital between 1985 and 2000. All patients had the histologic features of ectopic meningeal or glial tissue. Radiographic evaluations were available on all patients and the preoperative interpretations were compared to the intraoperative findings, particularily regarding the possibility of intracranial extension. The preoperative clinical diagnosis and postoperative histopathologic diagnoses were also compared.

All lesions were excised in a lenticular fashion with linear closure. Patients who had an intracranial extension had ligation of the rudimentary meningeal sac. Histologic sections from the lesions in 9 patients were available for review and analyzed with immunohistochemical staining, including epithelial membrane antigen (to delineate meningothelial cells), glial fibrillary acidic protein (to stain glial tissue), and synatophysin (to detect neurons).

RESULTS

There were 11 lesions in 10 patients (7 females, 3 males). The average age at excision was 8.6 months. Minimum follow-up time was 2 years for all patients. All lesions were midline, or near midline, and in the parietal/occipital scalp. Nine of 11 lesions (9 patients) had a "hair collar sign". Eight lesions had an associated capillary stain. All of the lesions were soft, nodular masses and most lesions were small, measuring 2 centimeters or less in circumference.

One patient had two lesions that were misdiagnosed as "dermoid cysts". The remaining lesions were accurately diagnosed preoperatively as cutaneous neural heterotopia (4 patients) or rudimentary meningocele (5 patients). All patients underwent preoperative radiographic evaluation. CT and/or MRI correctly predicted the presence of a calvarial defect in four patients. Plain radiographs, used exclusively in only one patient, showed no intracranial extension nor was a connection found intraoperatively. In the remaining 5 patients, CT and/or MRI imaging accurately predicted the absence of intracranial extension. Histopathologic examination demonstrated 8 lesions with heterotopic leptomeningeal tissue (positive EMA stain) and 3 lesions composed of glial tissue (positive GFA stain).

CONCLUSIONS

Heterotopic neural malformations are rare and clinical awareness of the entity is important to direct appropriate preoperative and intraoperative management. Preoperative imaging is essential to document possible intracranial involvement and avoid inadvertent dural penetration.