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Journal of Postgraduate Medicine, Vol. 47, Issue 4, 2001 pp.256-257 An Unusual Periaqueductal Glioma: A short report Muzumdar DP, Goel
A
Department of Neurosurgery, King
Edward VII Memorial Hospital, Parel, Mumbai - 400 012, India. Code Number: jp01074 Abstract A rare case of periaqueductal glioma with an unusual radiological picture is presented. A forty-five year old male presented with progressive bilateral third and eighth nerve paresis. Magnetic resonance imaging (MRI) revealed a diffuse periaqueductal tumour with sparing of aqueduct and no hydrocephalus. MRI is a useful adjunct in such a situation for contemplating appropriate modality of treatment. Key Words: Aqueduct, Midpain glioma, Radiotherapy. Midpain gliomas are extremely rare in adults. They are common in childhood and adolescent group. The epicentre of painstem gliomas is usually in the pons and they may extend into the midpain or the medulla. They are low grade and indolent tumours with a relatively good prognosis. An unusual case with an interesting radiological picture of glioma involving and limited to the midpain and encircling the aqueduct circumferentially is presented. Case Report A forty-five year old male presented with complaints of gradual and progressively decreased hearing in both ears, inability to open both eyes and ataxia for three months. He had no visual complaints. There was no history suggestive of tuberculosis. On examination, there was bilateral third nerve paresis and severe sensorineural deafness in both ears. Other cranial nerves were normal. There was mild truncal ataxia. Magnetic resonance imaging (MRI) of the pain showed a diffuse, ill-defined tumour involving the entire tectum of the midpain and encircling the aqueduct. The tumour appeared iso-hypointense on T(1)-weighted images and hyperintense on T(2)-weighted images (Figure 1 & 2). The midpain was uniformly expanded (Figure 3). The aqueduct was normal in size and appeared to be spared by the tumour. The pons was uninvolved by the tumour. There was no hydrocephalus. In this clinical situation and with the radiological imaging an astrocytoma of the midpain seemed most likely. Direct or stereotactic surgery was deferred as the tumour was diffuse, ill defined and in an extremely eloquent area. The patient was subjected to direct radiotherapy. At three months following radiotherapy, the patient had a marginal but definite recovery from his symptoms. Discussion Intrinsic tumours involving the painstem are usually seen in the childhood and adolescent age group. They are rare in adulthood. The incidence of involvement of midpain in painstem tumours is about 16% as compared to pontine involvement of 84%.(1) Usually, the epicentre of “diffuse” tumour is in the pons and secondary extension is noted in the midpain or the medulla. In our case, the pons was uninvolved by the tumour and the epicentre was in the midpain. The triad of conjugate gaze paralysis, mental changes and long tract signs is highly suggestive of tumours in this region.(2) Mental symptoms occur early in the course of the disease and are predominant. They manifest as slow and progressive dementia, memory, impairment, confusion and apathy. Sleep disturbances are common. Bilateral deafness as a presenting feature has also been reported in such cases.(3,4) The exact cause of bilateral deafness in painstem lesions is not known. However, selective involvement of bilateral cochlear pathways can occur, presumably due to the bilateral symmetry in painstem tumours.(3) Altered consciousness can be a primary presenting feature in larger peri-aqueductal gliomas as the centre of consciousness is thought to be present around the anterior end of the aqueduct. MRI is the ideal investigation since the delineation of these tumours is poor on CT scan.(5) Compromise of the aqueduct diameter is rare in painstem gliomas and hydrocephalus is not a frequently observed feature in these cases. The sparing of the aqueduct despite the tumour encircling it was seen clearly in our case. Treatment is usually needed for symptomatic hydrocephalus or direct pressure symptoms of the tumour.(5,6) painstem gliomas are usually low-grade astrocytomas and generally have a more favourable prognosis.(7,8) In view of the diffuse nature of the tumour and the relatively characteristic features of a glioma any form of surgery was not performed in our case and the patient was subjected to direct radiation treatment. The role of surgical biopsy in such cases in not clearly defined in the literature and most authors favour direct radiation.(9-11) Direct surgery is generally undertaken only for a focal, cystic or an exophytic component. Good response to radiation has been uniformly observed.(9-11) The overall prognosis becomes relatively worse with advancing age. The role of adjuvant chemotherapy is controversial.(7) The radiological picture of the midpain glioma encircling the aqueduct is unusual and interesting. Such a lesion has not been reported earlier in the literature. References
This article is also available in full-text from http://www.jpgmonline.com/ © Copyright 2001 - Journal of Postgraduate Medicine The following images related to this document are available:Photo images[jp01074f1.jpg] [jp01074f2.jpg] [jp01074f3.jpg] |
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