Low grade astrocytomas in the West of Scotland 1987-96: treatment, outcome, and cognitive functioning.

BACKGROUND: Low grade astrocytomas are among the most common central nervous system tumours in children. AIMS: To identify risk factors for the development of persistent intellectual handicap. METHODS: The notes of 30 children with histologically proven low grade astrocytoma who presented during the period 1987-96 were reviewed. Thirteen of these children who were diagnosed with intracranial tumours between 1992 and 1996 underwent cognitive assessment one year after the completion of treatment. RESULTS: Low grade astrocytomas were found in the cerebellum (59%), thalamus (17%), cerebral hemispheres (10%), and the cervical spinal cord (9%). Where possible all patients were treated with gross total resection of the tumour. Symptomatic children with tumours judged to be inoperable underwent biopsy followed by radiotherapy (13%). Three patients developed progressive disease following surgery and underwent repeat surgery and radiotherapy. Survival at a median follow up of 75 months (range 30-131) is 97%. At one year after the completion of treatment persisting cognitive impairment was common. The strongest predictor of IQ scores was the duration of symptoms of increased intracranial pressure preoperatively. CONCLUSIONS: Although the overall survival rate of children with low grade astrocytoma is excellent, significant long term disability occurs. Early diagnosis is essential to reduce postoperative cognitive morbidity.

Collagen vicryl--a new dural prosthesis.

No ideal dural grafting material is currently available. Many materials have been evaluated in this role, and for many neurosurgeons cadaveric human lyophilized dura has been popular. Recently this material has been putatively associated with Creutzfeldt-Jakob disease. In this study we compared three degradable materials, collagen vicryl (Bovine collagen coated vicryl mesh), Zenoderm (Porcine dermis) and Lyodura (Lyophilized human cadaveric dura) as dural substitutes. In an experimental model using the New Zealand White Rabbit the materials were implanted into dural defects of dimensions 1.7 cm by 1 cm. In the control group the dura was not repaired. In total 47 animals were used and sacrificed at time intervals of 2, 4, 8, 12, and 24 weeks. On gross examination the collagen vicryl produced few adhesions to the cerebral cortex and was replaced by a neomembrane which showed good union with the host dura. In the control group no new layer was formed and there were severe cortical adhesions. Zenoderm and Lyodura remained undegraded and produced more adherence to the cerebral cortex than the collagen vicryl implant. The histological examination showed collagen vicryl to support ingrowth of fibroblasts and the production of a new collagen layer which by 3 months resembled the original host dura. The inflammatory response to the implant did not persist after 3 months. The other substitutes were revitalized by host cells but remained undegraded at 6 months with ingrowth of woven bone and persistence of inflammatory and foreign body response. The results show collagen vicryl to be a suitable dural substitute with potential advantages over other currently used degradable materials, and should be evaluated more fully, both in laboratory studies and clinically.

Craniofacial osteotomies to facilitate skull base tumour resection.

In order to expose deeply situated tumours of the skull base in various regions, the concept of osteotomies of segments of the facial skeleton has been developed. The portion of skeleton overlying the tumour is removed, the lesion is resected and the removed bony structure is then reinserted. This has greatly facilitated tumour removal in difficult areas. The advantages of this approach are, to the surgeon, total en bloc resection of deeply situated tumours with few complications; for the patient, an improvement in the quality of the aesthetic result following resection of recurrent or potentially lethal tumours.

Treatment of tumors involving the anterior cranial fossa.

The potential for a tumor of the upper face, either malignant or nonmalignant, to involve the anterior cranial base is often not appreciated. This leads to inadequate preoperative investigation and to surgery performed by the head and neck surgeon without the help of the neurosurgeon. In this way, complete tumor resection may be compromised or delayed. Neither of these situations is desirable. If the potential for anterior cranial fossa invasion is recognized, there should be prior consultation with the neurosurgeon and a combined operative procedure. Exposure of these lesions has considerably improved with experience in congenital craniofacial deformities: this will allow en bloc resection of most pathologies. Immediate reconstruction after resection of nonmalignant tumors is advocated, but in aggressive--particularly in recurrent--malignancies, delayed reconstruction is advised. Careful combined follow-up with frequent blind biopsies should be carried out as indicated.

Frontonasal encephalocele--"long nose hypertelorism".

Two varieties of frontonasal encephalocele are presented, with variations in the surgical technique necessitated by the different anatomical findings. The encephalocele pushes the nasal skeleton posteriorly and caudally and widens the distance between the medial orbital walls. This causes the long nose and the telecanthus. In this variety of frontonasal encephalocele, hypertelorism is uncommon. There may be absence of dura in relation to the encephalocele. The suggested method of correcting the deformity involves a combined intracranial and extracranial approach. The nasal skeleton is mobilized and placed in its correct position and the telecanthus is corrected. All skull defects are bone grafted. Correcting the deformity at an early age is recommended.

A systematic approach to tumours of the base of the skull.

The base of the skull can be divided into three segments. This division allows a better understanding of the spread and the symptoms related to tumours in this area. Based on the location of the tumour, the surgical approach is varied. This systematic consideration allows for more efficient exploration of this difficult area by a combined plastic and neurosurgical approach. The types of tumours occurring in this area and their prognosis are discussed. A pre-existing craniofacial team experienced in the management of congenital craniofacial anomalies is an advantage when this type of procedure is done.