Oncogenic osteomalacia associated with a meningeal phosphaturic mesenchymal tumor. Case report.

A 60-year-old woman suffered from hypophosphatemic osteomalacia secondary to a frontal intracranial tumor. Oral administration of phosphate and 1-alpha-hydroxyvitamin D3 provided only temporary symptomatic relief. A computerized tomography (CT) scan of the patient's head revealed a large subfrontal tumor attached to the dura. Following removal of the tumor, the patient's hypophosphatemia subsided; her level of 1,25-dihydroxyvitamin D3, which was undetectable preoperatively, returned to normal, and she had symptomatic improvement. Three years later, decreasing levels of phosphate and 1,25-dihydroxyvitamin D3 indicated tumor recurrence, before it was detected by CT scan. Histological examination of the tumor provided the diagnosis of "mixed connective tissue variant of phosphaturic mesenchymal tumor." The characteristic histological features of this relatively rare entity are discussed. This is the first report of a surgically treated intracranial phosphaturic mesenchymal tumor that caused oncogenic osteomalacia.

Cavernous sinus neuroblastoma.

A case of cerebral neuroblastoma originating in the cavernous sinus is reported. The patient presented with a left cavernous sinus syndrome and the pathological diagnosis came as a histological surprise. Subtotal removal of the tumour and radiotherapy was followed by recurrence and led to re-operation. Postradiotherapy catecholamine level estimation prior to the second operative attempt showed a marked elevation. There is no other report of a primary cerebral neuroblastoma originating in any of the dural sinuses, and there are only 22 cases of cerebral neuroblastomas in adults reported previously. The primary cerebral or peripheral nature of this tumour was difficult to determine. The hypothesis of leptomeningeal nest cells of neural crest origin producing neuroblasts capable of neoplastic transformation, could provide an explanation for the unusual location of this tumour.

Multimodal imaging integration and stereotactic intracerebral electrode insertion in the investigation of drug resistant epilepsy.

Insertion of intracerebral electrodes for EEG recording is sometimes necessary during the pre-operative evaluation of patients with drug resistant epilepsy to define the site of seizure onsets. The precise and accurate placement of the electrodes requires a stereotactic technique of insertion based on correlated information derived from computerised imaging and stereotactic angiography. Described methods of multimodal stereotactic image integration present limitations in terms of satisfactory relocation and ability to spread data acquisition over a period of time. An alternative method of stereotactic acquisition of multimodal image information using the Gill-Thomas stereotactic repeat localiser is presented. Digital Angiographic (DSA), Computerised (CT) and Magnetic Resonance Imaging (MRI) data were correlated and used for target selection. The positional accuracy of the electrodes was confirmed repeatedly during the recording period with standard radiographic and MRI means and found to be satisfactory. There were no permanent complications in any of the patients included in the study. Stereoangiography correlative to computerised neuro-imaging offered a high degree of safety during the operation. Non-invasive relocation was an important feature of the combined system which was particularly helpful and duly appreciated by the patients. The temporal freedom provided during the investigative and operative period offers the advantage of an unhurried multi-image integration and targeting combined with less discomfort for the patient. The positional accuracy of the electrodes was easily verified during the post-operative period and this information added to the electroence-phalographic localising value of the technique.

Stereotactic insertion of intracerebral electrodes in the investigation of epilepsy.

Intracerebral electroencephalography is sometimes necessary in the pre-surgical evaluation of patients with drug-resistant epilepsy, in order to define the site(s) of seizure onset. Accurate depth electrode insertion would ideally require multimodal image integration, repetitive and non-invasive localization, assessment of positional accuracy and freedom in target and entry point selection. A method for the acquisition of the multimodal image stereotactic information, necessary for the precise targeting of the mesial temporal structures, and the operative technique used for the accurate placement of the intracerebral electrodes is described. The use of the Gill-Thomas (G-T) stereotactic repeat localizer offers the degree of temporal freedom during the data acquisition period of the electrode implantation procedure which leads to the advantage of an unhurried multi-image integration and targeting in any individual case combined with less discomfort for the patient. The integration of the G-T repeat localizing system with the existing components of the Cosman-Roberts-Wells (CRW-3) stereotactic system offers additional advantages. The target-centered arc-radius design allows complete freedom in the selection of the entry point, offers the possibility of multiple trajectories through the same entry point and permits a choice of either oblique or orthogonal lateral approaches, that are particularly useful for the electroencephalographic sampling of the posterior mesial temporal structures. The satisfactory localizing value of the technique and the additional advantage of easy confirmation of the positional accuracy of the electrodes during the postoperative period, using standard radiographic and magnetic resonance imaging studies, increases the potential of the technique for precise placement of depth electrodes during the pre-surgical evaluation of patients with epilepsy.

The far lateral approach for ventrally placed foramen magnum and upper cervical spine tumours.

Tumours of the foramen magnum region present a considerable surgical challenge. Their location combined with the close anatomical relation to sensitive and important vascular and nervous structures can make total removal difficult and sometimes impossible. Posterior and posteriolateral approaches, despite their simplicity, offer poor exposure and require retraction or rotation of the spinomedullary junction. Anteriolateral extrapharyngeal approaches are restrictive when a spacious superior exposure is necessary, while the vascular structures hidden by the tumours themselves appear only at the end of a rather tedious resection. The direct anterior transoral route, although effective for midline lesions, can be restrictive for laterally placed or broad-based tumours. A true lateral exposure provides an attractive alternative, the only anatomical obstacles being the horizontal part of the vertebral artery and the occipital condyle with its articulation with the lateral atlantal mass. A lateral approach was used in 15 patients with ventrally located tumours of the craniocervical junction, resulting in 12 total and three subtotal removals. In no case has there been inadequate tumour exposure and there were no complications of instability, CSF leak or infection directly related to the operation. Important advantages of the approach include: excellent exposure of the ventral spinomedullary junction, early and safe exposure of vascular structures, preservation of stability, minimal risk of infection, elimination of the need for neuraxis retraction and simplicity of instruments and technique.

The role of image-directed biopsy in the diagnosis and management of brainstem lesions.

The appreciation that brainstem tumours do not comprise a homogeneous pathological group and that up to 20% of the preoperative radiological diagnoses of brainstem lesions prove at operation to be wrong, has established the need for a firm histological diagnosis prior to treatment. Current neuro-imaging modalities may have increased the diagnostic accuracy and the detection rate of intrinsic brainstem lesions, but open exploration in cases without an exophytic component is still associated with a low diagnostic yield and considerable morbidity. A series of 72 brainstem lesions approached stereotactically with CT or MRI guidance is presented. A transcortical frontal precoronal trajectory was used in 58 and a suboccipital transcerebellar route in 14. Haematoma was diagnosed preoperatively in 16 cases and therapeutic aspiration was planned. In 56 cases the diagnosis was uncertain, although intrinsic tumour was suspected. A histological diagnosis was established in 52 cases, although in the remaining four cases a tumour was excluded. Unexpected findings occurred in over 15% of the cases. There were no operative deaths and the morbidity was low. In no case was there a permanent neurological deterioration directly related to the procedure, although there was a transient deterioration in two patients and another patient required early re-aspiration of a haematoma.

Early experience with the Gill Thomas Locator for computed tomography-directed stereotactic biopsy of intracranial lesions.

The Gill Thomas Locator is a stereotactic adaptor for the Brown-Roberts-Wells and Cosman-Roberts-Wells systems. It is a noninvasive device that relies on temporary fixation to the maxillary teeth. A series of 20 patients have had stereotactic biopsies with this system. A diagnostic biopsy was obtained in 19 cases. The frame was well tolerated, accurately relocatable, and allowed computed tomographic scanning and surgery to be conducted at different times.

Open stereotactic selective amygdalo-hippocampectomy for drug resistant epilepsy.

Selective removal of the medio-basal temporal structures has been introduced as an alternative to standard temporal lobectomy in the treatment of intractable temporal lobe epilepsy not related to gross structural lesions. Various approaches have been described for the surgical excision of the amygdalo-hippocampal complex, each of them presenting advantages and limitations. The recently introduced computer-assisted technique of volumetric stereotactic excision of deep-seated intracerebral lesions combines precision of targeting with elimination of unnecessary cortical trauma and may potentially provide an alternative method in the treatment of temporal lobe epilepsy. We present our experience of stereotactic volumetric selective amygdalo-hippocampectomy in six patients with medically intractable temporal lobe epilepsy. The criteria for selection, the pre-operative evaluation and the operative technique are discussed. All patients had a cessation or considerable reduction in seizure frequency while the morbidity was minimal.

Image directed stereotactic surgery for brain stem lesions.

Advances in neurological imaging may have increased the diagnostic accuracy and the detection rate of intrinsic brain stem lesions, but a histological diagnosis is still an essential requirement for rational and appropriate management. Open exploration allows biopsy and resection in cases where an exophytic component is present. The surgical inaccessibility and the resultant morbidity of these approaches, however, associated with a low diagnostic yield in cases with no visible surface abnormality, are important limiting factors. A series of 45 brain stem lesions stereotactically approached with CT or MRI guidance is presented. A transcortical frontal pre-coronal trajectory was used in all of them. Haematoma was preoperatively diagnosed in 10 cases and the procedure was for therapeutic aspiration. Of 35 cases where the diagnosis was uncertain, although intrinsic tumour was suspected, positive results were obtained in 33, while unexpected findings of granuloma, lymphoma, angioma, leucoencephalopathy, vasculitis and radiation necrosis were found in over 10% of the cases. There were no operative deaths and the morbidity was low. In no case was there a permanent neurological deterioration directly related to the procedure, although there was a transient deterioration in two patients and one patient required early reaspiration of a haematoma. Image directed stereotactic approaches to brain stem lesions can combine a high degree of accuracy (offering positive histological diagnoses) with a low operative morbidity. MRI directed biopsies can complement CT guided ones thus increasing the number of suitable cases and improving the success rate. The frontal precoronal transcortical trajectory provides safe access to the majority of the brain stem targets.

Multiple brain abscess: a review of fourteen cases.

The case notes of 14 consecutive patients with multiple brain abscesses presenting over a 14 year period were studied with respect to the incidence and presentation, the source of infection, the investigations, microbiology and the treatment and outcome. The incidence of multiple brain abscesses in non-immunocompromised patients is 13% of all intracranial abscesses. Computerized tomographic scanning is vital both in the detection of multiple abscesses and in the subsequent assessment of therapy. The source of infection in half of our patients was the teeth or the paranasal sinuses. Streptococci were isolated in 63% of the patients; staphylococci in 21%. This has obvious implications for the antibiotic policy. Intracranial surgery, with few exceptions, had a diagnostic and management role rather than a curative one; identification of the causative organism was its prime purpose. CSF, obtained by lumbar punctures, did not provide any positive cultures and should not be contemplated in view of the inherent hazards. The elimination of the primary focus of infection was a most important step in the management of this condition. Multiple brain abscesses represent a potentially curable condition, provided appropriate antibiotics are used, the primary septic focus is eliminated and the intracranial complications are anticipated by the use of frequently repeated CT scans.