The applicability of brain slice methodology to the study of focal cerebral ischaemia in the rat: an evaluation.

Brain slices were prepared from rats which had previously sustained a focal cerebral ischaemic insult as a consequence of middle cerebral artery occlusion. Slices cut in the coronal plane at the level of the anterior commissure were equilibrated for 1 h at 35 degrees C in a submersion chamber perfused with oxygenated artificial cerebrospinal fluid. A 4M K acetate-filled glass microelectrode (15-30 M omega) was used to penetrate each slice at multiple sites in order to record spontaneous neuronal activity. Subsequently, the presence of an area of cerebral infarction in the slices was confirmed using tetrazolium salt stains. Spontaneous neuronal activity, mainly as spike discharges or depolarisation, was observed in slices prepared from lesioned (6), sham-operated (6) and control (6) animals. The bursts of discharges were more consistently obtained and of larger amplitude and duration in the slices with focal areas of ischaemia when compared with the shams and controls. These observations may be of relevance to the hypothesis that excitotoxic discharges of disinhibited neurones contribute to the pathophysiology of stroke.

Rat middle cerebral artery occlusion: use of evoked potentials and tetrazolium staining to assess chronic ischaemia.

This study examined the effects of permanent, unilateral cerebral artery occlusion on the somatosensory evoked potential (SEP) recorded from the ipsilateral cortex in the anaesthetised rat. Ten days after artery occlusion the SEP was absent in the majority of rats tested and in the remainder the wave amplitude was reduced compared to the potential recorded from the normal hemisphere but latency was unaffected. Histochemical staining with Tetrazolium for infarct size has shown that loss of the SEP correlated with ischaemic damage to the cortex. SEP recording can be used to assess the extent of cortical ischaemia in this small animal model.

Analysis of the mechanism of action of bradykinin on human basilar artery in vitro.

Bradykinin (BK) initially produced concentration-related relaxations of human basilar artery in vitro. Concentration-effect curves constructed at 2 h intervals to BK over an 8 h period were reproducible. The rank order of potency of three kinins on the human basilar artery was found to be BK greater than methionyl-lysyl-BK greater than des-Arg9-BK. The B2-receptor antagonist Thi5,8, D-Phe7-BK but not the B1-receptor antagonist des-Arg9-Leu8-BK selectively blocked BK-induced relaxations of the human basilar artery. The relaxant effects of bradykinin and acetylcholine but not papaverine were attenuated after removal of the endothelium or treating the tissues with BW755C. Indomethacin was without effect. Concentration-effect curves to angiotensin I were markedly attenuated by captopril at a concentration which had no effect on BK, angiotensin II or 5-hydroxytryptamine responses. It is concluded that BK induced relaxations of the human basilar artery are mediated via activation of a B2 receptor and the response is dependent upon the release of a factor present in the endothelium. Angiotensin converting enzyme is present in the human basilar artery and is important for the conversion of angiotensin I to angiotensin II but apparently not for the degradation of BK. It is likely that other kininases are present and active in the tissue.

Arnold-Chiari malformation. Review of 71 cases.

The natural history of symptomatic adult Type I Arnold-Chiari malformation (ACM) is variable, and the value of surgery in the management of this disease is difficult to assess. A series of 71 patients in whom a diagnosis of Type I ACM was confirmed at operation is presented, and the progress of the patients following posterior fossa decompression is analyzed. The length of history varied greatly. Pain was the commonest symptom (69% of patients); other symptoms included weakness (56%), numbness (52%), and unsteadiness (40%). The presenting physical signs consisted of a foramen magnum compression syndrome (22%), central cord syndrome (65%), or a cerebellar syndrome (11%). Myelography was performed in 69 patients, and was the most useful investigation. Only 23% of plain radiographs were abnormal. In addition to tonsillar descent, the operative findings included arachnoid adhesions (41%) and syringomyelia (32%). All patients underwent suboccipital craniectomy and C1-3 laminectomy. Respiratory depression was the most frequent postoperative complication (14%), and one patient died from sleep apnea. Early postoperative improvement of both symptoms (82%) and signs (70%) was followed by later relapse in 21% of patients, showing an initial benefit following surgery. None of the patients with a cerebellar syndrome deteriorated, whereas 56% of patients with evidence of foramen magnum compression and 66% of those with a central cord syndrome maintained their initial improvement. The authors conclude that posterior fossa decompression appears to benefit some patients, although a significant proportion might be expected to relapse within 2 to 3 years after operation, depending upon the presenting syndrome.

Ventriculoperitoneal shunt procedure complicated by ureter obstruction. Case report.

The authors present the case history of a patient in whom the peritoneal catheter of a ventriculoperitoneal shunt system caused ureter obstruction. This is a rare complication of such a shunt procedure, and the patient's symptoms were relieved by shortening the peritoneal catheter.

Trigeminal nerve tumor: comparison of CT and MRI. Case report.

Benign tumors of the middle fossa components of the trigeminal nerve are rare. The authors describe the case history, radiological investigation, and operative findings of a patient with a large trigeminal neurofibroma of the middle fossa. The unusual mode of presentation is discussed. Valuable information was provided by magnetic resonance imaging prior to successful removal of this tumor.

Effect of fibrin-fibrinogen degradation products on human basilar artery preparations.

Experiments were performed to determine the effects of fibrin-fibrinogen degradation products on the human basilar artery in vivo. Citrated plasma and streptokinase were incubated at 37 degrees C to produce a preparation of fibrinogen degradation products. Aliquots of the incubate were obtained at 90 minutes, 48 hours, and 1 and 2 weeks after preparation, and were separated into fractions of different molecular weight (MWt), using an ultrafiltration technique. Each fraction was tested at each of the above times for contractile activity and possible interaction with a threshold concentration of 5-hydroxytryptamine (5-HT) on the human basilar artery. Contractile activity was initially confined to the 90-minute aliquot fraction MWt greater than 100,000, but as the incubation proceeded, such activity was also seen in the lower MWt fraction less than 100,000 greater than 10,000 at all time intervals. This activity was never seen in the fraction MWt less than 10,000 at any time. Enhancement of the 5-HT response was initially confined to the higher molecular weight fractions, but after 48-hour incubation all fractions showed this activity. It is suggested that products of fibrin-fibrinogen degradation may be involved directly or indirectly in influencing the pathophysiological mechanism(s) responsible for cerebral arterial spasm following subarachnoid hemorrhage.

Facial nerve preservation during surgery for removal of acoustic nerve tumors.

A series of 33 patients with 35 acoustic nerve tumors is reviewed. Tumor size was estimated from computerized tomography (CT) scans, and its influence on anatomical and functional preservation of the facial nerve was assessed. Six tumors (one invading the petrous bone, three medium and two large tumors) were not detected on CT scans. The translabyrinthine approach was used in seven instances (one small and six medium tumors) and the suboccipital transmeatal approach for 28 tumors (seven medium and 21 large tumors). Anatomical preservation of the facial nerve was achieved in 83% of operations for tumor removal, two of which were subtotal. A further two patients underwent subtotal removal, but the facial nerve was destroyed. Large tumors carried an increased risk of damage to the facial nerve, but even in this group the nerve was preserved anatomically intact in 70% of cases. Damage to the facial nerve occurred more frequently in patients with preoperative evidence of facial weakness; however, this factor did not appear to influence functional recovery of the facial nerve, provided that the nerve was intact at the end of the operation. A simple grading system for facial nerve function is described. Ony 76% of anatomically intact facial nerves showed any evidence of function 1 month after surgery. Postoperatively, facial function improved with time. At the latest review, 45% of these patients had normal facial function or mild facial weakness (Grades I and II).

Intravenous digital subtraction angiography in intracranial aneurysms.

Intravenous digital subtraction angiography was undertaken in 121 patients with known intracranial aneurysms. Its role in the management of these patients and its diagnostic accuracy have been assessed.

Magnetic resonance imaging of acoustic neuromas: the role of gadolinium-DTPA.

Magnetic resonance imaging (MRI) was performed in 20 patients with evidence on computed tomography (CT) of 21 acoustic neuromas before and after intravenous administration (0.1-0.2 mmol/kg body weight) of gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA). Multi-section spin-echo (SE) sequences of varying repetition (TR) and echo (TE) times were performed in the transverse and coronal planes with a section thickness of 10 mm. All acoustic neuromas displayed marked enhancement on the T1-weighted (short TR/TE) SE sequence post-Gd-DTPA. The intrameatal component was particularly well demonstrated compared with non-enhanced magnetic resonance (MR) images and contrast-enhanced CT. Identification of intrameatal tumour was difficult on T2-weighted SE images and one tumour was not identified on the T1-weighted SE sequence prior to Gd-DTPA. Four of five intrameatal tumours measuring less than 8 mm could only be demonstrated on CT by using CT air meatography. Extrameatal tumour extension was demonstrated on contrast-enhanced CT, although the assessment of brain-stem involvement and displacement was not as clearly seen as on coronal MR images. In two patients with large acoustic neuromas and a cyst, the true relationship of the cyst to the tumour could only be identified on the post-Gd-DTPA scan. Magnetic resonance imaging with gadolinium-DTPA is a relatively quick, safe, well tolerated and effective method for the diagnosis of acoustic neuroma.

Computer graphics in the assessment of severity of spasmodic torticollis: potential role in the evaluation of surgical treatment.

There is a need for objective evaluation of the effectiveness of treatment of spasmodic torticollis so that comparisons can be made between different therapies. Video tape recordings of patients undergoing surgery for spasmodic torticollis were digitized and the movement of a reference marker was tracked by computer. A graphic presentation of oscillation of the marker around a mean position was obtained. Comparison of preoperative and postoperative recordings enabled assessment of the effectiveness of surgery. The results can be tabulated, facilitating accurate documentation of large series of results in publication. This should enable easier comparison of the effectiveness of different therapies.

Recurrence of meningiomas after operation.

The authors reviewed 53 consecutive patients who underwent surgical removal of a meningioma within a 10-year period. The removal was graded macroscopically as either a total removal (types I-III) or a subtotal removal (type IV). The patients were observed for an average period of 5.3 years, during which time there was a 9.5% recurrence after type I removals and an 18.4% recurrence after type II. There was regrowth in 20% of the subtotal group. There was no correlation with age or sex, but histology was important. Syncytial tumors tended to recur, and mitosis and area of focal necrosis were associated with a tendency towards recurrence. The significant features associated with recurrence are discussed.

Ionomeric bone cement in neuro-otological surgery.

The use of a polymaleinate glass ionomer cement in 80 neuro-otology cases is described. It has proved of great value in translabyrinthine acoustic neuroma surgery, reducing the incidence of CSF fistula to nil. It is the method of choice for fixation of the Nucleus cochlear implant, and has many other applications in the field of otology and neuro-otology. It is easy to use and appears to have no side effects.

An unusual posterior cranial fossa tumour causing hearing loss.

Clivus meningioma is an uncommon tumour arising from the region of the synchrondrosis between the basal portions of the sphenoid and occipital bones. We report a case of a patient with a large meningioma of the clivus whose presenting symptom was auditory change. Alteration of hearing is a rare mode of presentation for such a tumour although it may present at a later stage in about 50 per cent of cases. The discrepancy between the size of the tumour and the paucity of physical findings, the value of a multiple test auditory screening strategy, and the surgical approach in this case are discussed.

Spontaneous dissection of the intrapetrous internal carotid artery.

Two cases of cervicocephalic arterial dissection of the intrapetrous carotid artery are described. One patient presented with intolerable objective pulsatile tinnitus, the other with a cerebral infarction. Both were successfully treated with anticoagulants. The significance of minor degrees of trauma and of neck extension in the aetiology of these apparently spontaneous lesions is discussed.

Haemangiopericytoma of the temporal bone.

Haemangiopericytoma is an uncommon vascular tumour with a widespread distribution. Although meningeal involvement is well recognized, only a few sporadic cases of temporal bone lesions have been documented, all with doubtful sites of origin. Late presentation together with the restrictive anatomy of this region often precludes its effective removal and even minimal residual disease may progress rapidly. A series of three such patients are presented in order to discuss the natural history, histological features and treatment of this disease.

Variation of expression of the gene for type 2 neurofibromatosis: absence of a gender effect on vestibular schwannomas, but confirmation of a preponderance of meningiomas in females.

Type 2 neurofibromatosis is a dominantly inherited disorder in which the great majority of sufferers develop bilateral vestibular schwannomas. In a UK study of 183 individuals from 112 families we have previously shown a fairly similar disease course within families, but quite marked inter-familial variation. We have confirmed an increase in severity when the gene is inherited from an affected mother, but evidence that women are more severely affected than men is lacking. Age at onset of symptoms, of deafness and at diagnosis are identical for the entire dataset and for a comparison of 10 male/female sibling pairs. Only three out of 42 pregnancies in symptomatic women were accompanied by a reversible worsening in symptoms due to vestibular schwannomas. Of 328 consecutive cases of unilateral vestibular schwannoma, there was no significant difference in the sex ratio or size. There now appears to be little evidence for a female hormonal effect on vestibular schwannomas. However, females with type 2 neurofibromatosis have significantly more meningiomas.

Criteria for hearing preservation in acoustic schwannoma surgery: the concept of useful hearing.

In the quest for hearing preservation in patients with acoustic schwannomas it is essential that surgeons do not lose sight of the concept of 'useful' hearing. There is an important difference between hearing preservation which pleases the surgeon and that which will be appreciated by the patient. Tumour size, pure tone audiogram average differences between ears and speech discrimination scores have been recorded in a series of 114 patients with unilateral acoustic schwannomas. Criteria for useful hearing are presented in terms of pure tone audiogram average difference and speech discrimination scores. There were 11 patients (10 per cent) with a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 30 dB or better and a tumour size of no more than 2 cm. Only one patient (0.9 per cent) had a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 20 dB or better and a tumour size of no more than 1 cm. It is concluded that hearing preservation techniques may be applicable to between 1 and 10 per cent of patients with unilateral acoustic schwannomas.

Oestrogen and progesterone receptors in acoustic neuroma.

Tissue samples from fourteen consecutive (8 male: 6 female) acoustic neuromas were assayed for hormone receptors using either a monoclonal antibody (MA), dextran coated charcoal (DCC) or isoelectric focusing (IEF) technique. In this series there were no unequivocally positive results, a finding at variance with previously published results.

Audio-vestibular manifestations of Chiari malformation and outcome of surgical decompression: a case report.

Sensorineural hearing loss, tinnitus, dizziness and ataxia are recognised symptoms associated with Chiari malformations but they are rarely the presenting complaints. Patients with such symptoms are frequently referred to otolaryngologists and audiological physicians. We report a case of a 13-year-old girl who presented complaining of tinnitus and impaired hearing, and was subsequently diagnosed as having a type I Chiari malformation. Pure tone audiogram showed a mild hearing impairment on the left side and the speech audiogram was normal. Auditory brain stem responses and the electronystagmography were abnormal. The patient underwent posterior fossa decompression following which her tinnitus disappeared, the hearing problem recovered and some of the abnormal electrophysiological parameters were corrected.