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Solitary cysticercus granulomas that produce seizures usually measure less than 20 mm in diameter and diminish in size spontaneously. Unlike live cysticercus cysts, they have not been known to increase in size. In a prospective follow-up study of 93 consecutive patients with epilepsy and small solitary lesions (< 20 mm in diameter) enhancing on computerized tomography (CT), 91 were found to have solitary cysticercus granuloma; of these, seven (7.7%) were diagnosed as having an enlarging cysticercus granuloma. Enlarging lesions were defined as those that, on follow-up CT, had increased by more than 50% of their original size but were still less than 20 mm in diameter (Group 1, three patients) or those that had increased to more than 20 mm (Group 2, four patients). Excision biopsy is recommended for Group 2 solitary lesions, regardless of the clinical progression, to eliminate the possibility of other pathologies. However, a trial of albendazole therapy with early CT re-evaluation (within 4 to 6 weeks) may be warranted in those with Group 1 lesions and in selected patients with Group 2 lesions. It is important to recognize the entity of enlarging solitary cysticercus granuloma to avoid mistaking it for a tuberculoma and treating the patient with empiric antituberculous therapy.

The brain stem is an unusual location for a pyogenic abscess. We report a case of a brain stem abscess in a 5-year-old boy with tetralogy of Fallot that was refractory to conservative medical therapy but was cured after a single computed tomographic-guided stereotactic aspiration and appropriate antibiotic therapy. The remarkable features in this case were the extremely large size of the abscess (3.2 cm in diameter), occupying the full vertical extent of the brain stem and containing 15 ml of pus. We believe this is the first report of a favorable outcome in a cardiogenic brain stem abscess. The value of computed tomographic-guided stereotactic surgery in the management of this lethal condition is documented with a review of the relevant literature.

The main objective of our study was to evolve a practical management protocol for neurosurgical patients with hyponatremia and natriuresis, based on their blood volume status and hematocrit. Twenty-one patients with hyponatremia and natriuresis and 3 control patients were studied. Patients with hyponatremia were categorized on the basis of their hematocrit, central venous pressure, and total blood volume. Group A consisted of patients with hypovolemia and anemia (16 patients); Group B patients had hypovolemia but no anemia (5 patients); Group C included those with hypervolemia (0 patients). Patients in Groups A and B received isotonic saline (> 50 ml/kg/d) and oral salt (12 g/d). Additionally, those in Group A were transfused with 500 ml of whole blood. The end points in the study were 72 hours after entry or two consecutive serum sodium values of > 130 mEq/L, whichever was earlier. Hyponatremia was corrected in all the patients within 72 hours (1 patient, < 24 h; 13 patients, < 48 h; and 7 patients, < 72 h). We conclude that most neurosurgical patients with hyponatremia and natriuresis have hypovolemia, with or without anemia. Fluid and salt replacement and a blood transfusion rather than fluid restriction often results in the correction of the hyponatremia. Our findings offer indirect evidence to support the hypothesis that in most of these patients, hyponatremia is caused by cerebral salt wasting syndrome, rather than the syndrome of inappropriate secretion of antidiuretic hormone.

The neurosurgical manifestations in three patients with sphenoid sinus mucoceles and two others with fronto-ethmoidal mucoceles are presented. In two patients, sphenoid sinus mucoceles produced visual loss while in the other severe headache was the only symptom. Both patients with fronto-ethmoidal mucoceles presented with proptosis. All patients had surgical treatment. While other symptoms were relieved following treatment, visual loss remained unchanged in both patients in whom it was present. We recommend a high level of suspicion for mucoceles as a cause of sudden or progressive visual loss. Prompt surgical therapy is needed to achieve good visual outcome.

Nondiagnostic biopsies were analyzed in a consecutive series of 407 patients undergoing computerized tomography (CT)-guided stereotactic biopsies. These were categorized as either negative biopsies, when normal tissue or nonspecific pathology was found, or inconclusive, when a definitive diagnosis could not be made although representative tissue was obtained. Nineteen biopsies (4.7%) were negative and 10 (2.4%) were inconclusive, giving an overall nondiagnostic biopsy rate of 7.1% (29 of the 407 cases). Suspected neoplastic masses (390 cases) were classified on the basis of their CT morphology into four groups: Group 1 included purely hypodense nonenhancing masses; Group 2 included isodense nonenhancing masses; Group 3 included ring-enhancing masses; and Group 4 included mixed-density enhancing masses. Although a higher proportion of hypodense nonenhancing masses (six of 56, or 10.7%) yielded a negative result, there was no statistically significant difference in the negative biopsy rates for the different CT categories (p = 0.06). The negative biopsy rates for the 6 years of the study, 1987 to 1992 (1987 being an incomplete year) were as follows: 13.3%, 6%, 3.2%, 3%, 5.8%, and 2.7%. There was no significant decrease in the negative biopsy rate as experience with this procedure increased (p = 0.20). A total of eight surgeons independently performed the biopsies. There was no significant difference (p = 0.24) in the negative biopsy rate of the surgeon with the most experience (124 biopsies, 2.4% negative biopsy rate) compared with that of the seven other surgeons combined (283 biopsies; 5.7% negative biopsy rate). These findings suggest that the yield in a stereotactic biopsy is independent of the CT appearance of the mass. Adherence to certain basic principles in patient and target selection will ensure a reasonable percentage of positive yield with stereotactic biopsy procedures even if the surgeon is relatively inexperienced. There does not appear to be a learning curve in the performance of CT-guided stereotactic biopsies. The management of patients with nondiagnostic biopsies is discussed.

The aim of this paper is to present our experience with CT guided stereotaxy, documenting the types of procedures performed and their outcome. Over the past five and a half years, 600 stereotactic procedures have been performed using the Brown Roberts Wells (BRW) stereotactic system. The procedures were categorized as (i) diagnostic biopsies : 431; (ii) Therapeutic procedures (Aspirations) : 52; (iii) functional procedures: 13; and (iv) stereotactic craniotomies: 104. False negative or nondiagnostic biopsies were obtained in 28 out of 431 diagnostic procedures (6.5 percent) and in 3 cases the procedure was terminated without taking a biopsy. Two of 483 patients undergoing stereotactic biopsy or aspiration died due to procedure related complications (0.41 percent). Seven patients had major morbidity associated with this procedure (1.44 percent) and 12 others had transient worsening of neurological status (2.48 percent). All functional procedures were done for movement disorders. Stereotactic craniotomies were performed for excision of small lesions in eloquent areas. Of 600 procedures, the preoperative objective was achieved in 564 cases (94 percent). Stereotactic surgery has very low mortality and morbidity and plays an important role in the management of intracranial lesions.

Tuberculous spinal arachnoiditis (TSA) is a serious condition and its early diagnosis is imperative. This communication is on 3 patients in whom the computerised tomography (CT) and water soluble myelographic appearance in TSA is highlighted. In twopatients, this was found to be superior in the diagnosis of TSA than plain myelography. On CT-myelography, TSA is characterised by a 'beaded' appearance and a denser concentration of the contrast medium in the ventral subarachnoid space.

We treated 11 patients with a persistent (> 3 months), solitary small cysticercus granuloma and seizures with albendazole in a daily dose of 15 mg/kg body weight for 14 days. At repeat CT examinations performed at intervals of 2.5 to 6 weeks after initiation of therapy, the lesions had resolved in two patients and become significantly smaller (less than 50% of their pretreatment size) in two. Albendazole therapy in responders hastened the resolution of the lesions and confirmed the diagnosis.

It is commonly believed that differentiating solitary small cysticercus granulomas and small tuberculomas in patients with seizures is difficult without resorting to an excision biopsy. The aim of this study was to formulate clinical and computerized tomography (CT) criteria to distinguish these two entities in patients with epilepsy. Toward this end, clinical and CT data from six consecutive patients with histologically proven small solitary tuberculomas and 25 consecutive patients with histologically proven solitary cysticercus granulomas were compared. Evidence of raised intracranial tension and a progressive focal neurological deficit was seen only in patients with tuberculomas (two of six cases). All tuberculomas were greater than 20 mm in size and five of the six were irregular in outline. Only tuberculomas were associated with a midline shift on CT (four of six cases). All cysticercus granulomas were less than 20 mm in size and 24 (96%) of the 25 were regular in outline, conforming to one of two characteristic patterns. No cysticercus granuloma was associated with a midline shift. Based on the above clinical findings (evidence of raised intracranial tension and a progressive neurological deficit) and CT criteria (size, shape, and association with a midline shift), it is possible to separate these two entities in a majority of patients with seizures and with a single small lesion on CT.

CT-guided stereotactic techniques were used in the management of 21 patients (22 procedures) with intracranial tuberculomas. In 17 patients CT-guided stereotactic surgery was performed to obtain a diagnosis; 10 patients with small superficial lesions or masses in eloquent areas had an excision biopsy following CT-guided stereotactic craniotomies (Group A); seven patients underwent a closed stereotactic biopsy (Group B). Four patients (five procedures) with previously proven tuberculous disease had stereotactic aspiration of a cystic tuberculous mass (Group C). All patients in Group A had a definite histological diagnosis of a tuberculoma. Of the seven in Group B, a definitive diagnosis was obtained in two; in four patients the biopsy showed evidence of chronic inflammation; and in one the procedure was abandoned due to venous hemorrhage. All patients in Group C had amelioration of their symptoms following aspiration of the contents of the cystic mass. There was transient operative morbidity in two patients. There was no procedure-related permanent disability or mortality. CT-guided stereotactic biopsy being minimally invasive, is ideally suited for the management of deep-seated intracranial tuberculomas as they can be treated medically once a diagnosis is secured. A diagnosis of chronic inflammation obtained on CT-guided stereotactic biopsy, in correlation with the clinical and radiological findings, often provides confirmatory evidence of a tuberculoma in a patient with an intracranial mass. It also rules out a neoplasm and avoids empiric therapy of brain masses. Stereotactic localization techniques also help avoid possible morbidity associated with the excision of superficial small tuberculomas from eloquent areas.

Tuberculous atlanto-axial dislocation is an uncommon disease. Five of six patients with tuberculous atlanto-axial dislocation were successfully managed using different strategies. The advantages and disadvantages of these different protocols and their appropriateness in a particular clinical situation are discussed.

Cystic cerebellar schwannoma is a rare tumour which may not be considered when a low attenuation computed tomographic (CT) lesion is seen in the cerebellar parenchyma. Since the origin of the Schwann cell in the cerebellar parenchyma is conjectural, immunohistochemical techniques are necessary for a diagnosis.

Continuous monopolar impedance monitoring was performed during CT-guided stereotactic procedures involving 46 probe passages in 33 patients. Four readings were obtained during each passage to the lesion corresponding to the gray matter (A), subcortical white matter (B), perilesional tissue (C), and the target (D). The mean impedance of low-grade gliomas (442.7 +/- 96.1 SD ohm) was lower than that of high-grade gliomas (675 +/- 67.3 SD ohm) (p = 0.01). But because of considerable overlap of values in the 400-700 ohm range only impedances of less than 400 ohm and greater than 700 ohm are capable of predicting pathology, the former being associated with low-grade gliomas and the latter with high-grade gliomas. The mean change in impedance from the perilesional tissue to the target (C-D) was higher for cystic lesions compared with the solid lesions (127.5 +/- 131.5 SD versus 78.9 +/- 72.4 SD ohm) but was not statistically significant (p = 0.148). Impedance monitoring was found to be particularly useful in determining the entry into thick-walled cysts. It also helped elucidate the structures encountered in the probe track. Overall this procedure is a simple and useful adjunct, which can enhance the accuracy of selected CT-guided procedures without unduly increasing the length of the procedure or altering the morbidity.

We reviewed the results of ventriculostomy with external ventricular drainage in patients with acute hydrocephalus complicating subarachnoid haemorrhage. Of 194 consecutive patients with subarachnoid haemorrhage admitted during the past eight years, 52 (27%) developed hydrocephalus within 72 hours of the ictus. Patients with acute hydrocephalus were in grades III to V (Hunt and Hess) at the time of evaluation and all patients with hydrocephalus underwent ventriculostomy within 24 hours of diagnosis. Twenty-six patients improved within 24 hours of cerebrospinal fluid drainage and 17 of these patients underwent surgery, nine of whom did well (Glasgow Outcome Scale 1 and 2). All 18 patients who did not improve within this period, including one who worsened, died. In eight patients the response to ventriculostomy was considered as undetermined, because of the proximity of the drain insertion to a definitive surgical procedure, and all of them had an excellent outcome (Glasgow Outcome Scale 1). Of 32 patients in grades IV and V, 17 did not improve and all of them died. Eight of the 15 patients in these grades, who were in the improved or undetermined categories, did well. Five patients (10%) developed meningitis. All patients with this complication had drainage for more than four days. Seven patients (14%) had a rebleed during the drainage. All except one patient with a rebleed had no surgery or delayed surgery and in six of them recurrent haemorrhages occurred after more than 24 hours of drainage. We conclude that routine ventriculostomy with external ventricular drainage should be considered for all patients with altered sensorium and acute hydrocephalus following subarachnoid haemorrhage.(ABSTRACT TRUNCATED AT 250 WORDS)

The study describes the microsurgical neurovascular relationships of the root entry zone of lower cranial nerves in 23 cadavers. The vessel type, frequency of contact and site of contact on the root entry zone were analysed. Three types of vascular patterns (Types I-III) were found. Facial nerve: frequency of contact 31.8%; arterial contact 92.9%, Type I (lying across) 78.9%; anterior inferior cerebellar artery in 84.6%. Glossopharyngeal nerve: frequency of contact 23.9%; arteries 54.5%, veins 45.5%; posterior inferior cerebellar artery in 83.3% and Type II (loop) 50.1%. Vagus nerve: frequency of contact 26.1%, arteries 58.3%. Types II and III (passing through) formed 42.9% each. Hypoglossal nerve: frequency of contact 78.2%; vertebral artery 88.9%. No 'grooving' on any nerve was seen. Hence, 'contact' by a vessel at the root entry zone may not be significant in the etiology of lower cranial rhizopathies.

Hydrocephalus is a common complication of tuberculous meningitis. Case studies of 114 patients with tuberculous meningitis and hydrocephalus, who underwent shunt surgery between July, 1975, and June, 1986, were reviewed to evaluate the long-term outcome and to outline a management protocol for these patients based on the results. Seven factors were studied in each case: 1) age at admission; 2) grade on admission (I to IV, classified by the authors; Grade I being the best and Grade IV being the worst); 3) duration of alteration of sensorium; 4) cerebrospinal fluid (CSF) cell content at initial examination; 5) CSF protein levels at initial examination; 6) number of shunt revisions required; and 7) the necessity for bilateral shunts. During a long-term follow-up period ranging from 6 months to 13 years (mean 45.6 months), the mortality rate was 20% for patients in Grade I; 34.7% for patients in Grade II; 51.9% for patients in Grade III; and 100% for patients in Grade IV. Only the grade at the time of admission was found to be statistically significant in determining final outcome (p less than 0.001). Based on these results, the authors advocate early shunt surgery for Grade I and II patients. For patients in Grade III, surgery may be performed either if external ventricular drainage causes an improvement in sensorium or without selection. All patients in Grade IV should undergo external ventricular drainage and only those who show a significant change in their neurological status within 24 to 48 hours of drainage, should have shunt surgery.

When used as a prophylactic measure and in chronic experiments, omental transposition has been shown to reduce ischaemic and traumatic oedema in the spinal cord and ischaemic oedema in the brain. We designed this experiment to evaluate the acute effects of a pedicled omental graft on cold-induced brain oedema in cats. Focal oedema was induced in the left frontoparietal region of the brain of nine anaesthetized cats. In five cats, a laparotomy was done and a pedicled omental graft was placed on the lesioned left hemisphere immediately after the cold lesion was made. All cats were sacrificed 72 hours later, and the water content of the white matter was determined in the lesioned and the normal hemispheres. The mean water content of the lesioned hemisphere of the treated group of animals was not significantly different from that of the control group. We conclude that a pedicled omental graft failed to reduce vasogenic oedema in an acute model and probably has no role in the acute management of brain oedema.

Empiric therapy, especially antituberculous therapy, is frequently given to Indian patients with brain masses. This report documents our experience in avoiding such therapy using CT-guided stereotaxy. Out of 101 procedures done on 99 patients with brain masses, 80 were done to obtain a histological diagnosis and 21 for therapeutic purposes. There was no mortality and 2% morbidity. A positive diagnosis was obtained in 94% (75/80) of patients undergoing a biopsy. Diagnosis of tuberculous lesions was based mainly on the presence of acid-fast bacilli in the biopsy specimen or pus. In six patients the radiological diagnosis was wrong and in one the diagnosis was not certain. Inappropriate therapy was given to three patients, on the basis of a CT or MRI scan, before a biopsy was done. It is essential that a histological diagnosis be obtained in all patients with brain masses and there is no role for empirical therapy except in isolated cases.

A patient with an acquired basilar impression, due to a cavernous angioma involving the skull base, is presented. The various causes of acquired basilar impression are reviewed.

The authors describe an unusual case of a primary chondroid chordoma arising from the base of petrous temporal bone. The patient, a young male, presented with a left sided jugular foramen syndrome. The CT findings of a tumour arising from the base of the left petrous temporal bone were confirmed at infratemporal exploration. The clinical and histopathological and immunohistochemical differences between classical (typical) chordoma and its chondroid variant are highlighted. The rarity of primary chordomas at this site is stressed.

Non-traumatic cerebrospinal fluid (CSF) rhinorrhea is an uncommon condition. 15 patients with non-traumatic CSF rhinorrhea having "normal pressure leaks" are presented. Metrizamide CT cisternography failed to reveal the site of the fistula in 3 patients. 11 of the 15 patients underwent surgery for closure of the fistulous communication. In 8 of them the fistula was in the anterior fossa, in one it was in the sellar floor and in two the fistula site was not seen either radiologically or at surgery. In all except the one patient with sellar floor defect an intracranial approach was used. 12 patients have been followed up for 6 months to 9 years and 10 (83%) have been cured of their rhinorrhea. The intracranial approach is preferred to an extracranial approach in the repair of anterior fossa fistulae. Conservative treatment may be effective in selected patients.

A patient with an intracavernous carotid aneurysm usually presents with symptoms and signs of a space occupying lesion, producing one of a variety of types of cavernous sinus syndromes (Jefferson, 1938). Epistaxis is an unusual feature in these patients and when present is nearly always associated with a traumatic aneurysm (Mahmoud, 1979). There are only two reported cases of non-traumatic intracavernous carotid aneurysms presenting with epistaxis and diagnosed during the lifetime of the patient (Troupp, 1962; Labayle and Legent, 1964). The authors present a third such case. The importance of considering aneurysms in the differential diagnosis of epistaxis is emphasised. The radiological investigations and management of these patients is discussed.