T. Pietilä

Ruptured intracranial dermoid cysts.

BACKGROUND Intracranial dermoid cysts are rare congenital neoplasms that are believed to arise from ectopic cell rests incorporated in the closing neural tube. The rupture of an intracranial dermoid cyst is a relatively rare event that typically occurs spontaneously. In the past it was believed that rupture is always fatal, a hypothesis that is not supported by more recently reported cases. The symptoms associated with rupture vary from no symptoms to sudden death. METHODS The present paper analyzes published cases of ruptured intracranial dermoid cysts in terms of their age profile and their clinical presentation and describes an additional case. RESULTS Analysis of published cases revealed headache (14 out of 44 patients; 31.8%) and seizures (13 out of 44 patients; 29.5%), to be the most common signs of rupture followed by, often temporary, sensory or motor hemisyndrome (7 out of 44 patients; 15.9%), and chemical meningitis (3 out of 44 patients; 6.9%). CONCLUSION Headache occurred primarily in younger patients (mean age 23.5 +/- 9.3 years), whereas seizures primarily occurred in older patients (mean age 42.8 +/- 11.3 years). The patients with sensory or motor hemisyndrome associated with rupture of an intracranial dermoid cyst showed a more homogeneous age distribution (mean age 38.4 +/- 23.5 years).

Intraoperative microvascular Doppler ultrasonography in cerebral aneurysm surgery

OBJECTIVES Outcome of surgical treatment of cerebral aneurysms may be severely compromised by local cerebral ischaemia or infarction resulting from the inadvertent occlusion of an adjacent vessel by the aneurysm clip, or by incomplete aneurysm closure. It is therefore mandatory to optimise clip placement in situ to reduce the complication rate. The present study was performed to investigate the reliability of intraoperative microvascular Doppler ultrasonography (MDU) in cerebral aneurysm surgery, and to assess the impact of this method on the surgical procedure itself. METHODS Seventy five patients (19 men, 56 women, mean age 54.8 years, range 22-84 years) with 90 saccular cerebral aneurysms were evaluated. Blood flow velocities in the aneurysmal sac and in the adjacent vessels were determined by MDU before and after aneurysm clipping. The findings of MDU were analysed and compared with those of visual inspection of the surgical site and of postoperative angiography. Analysis was also made of the cases in which the clip was repositioned due to MDU findings. RESULTS A relevant stenosis of an adjacent vessel induced by clip positioning that had escaped detection by visual inspection was identified by Doppler ultrasonography in 17 out of 90 (18.9%) aneurysms. In addition, Doppler ultrasound demonstrated a primarily unoccluded aneurysm in 11 out of 90 (12.2%) patients. The aneurysm clip was repositioned on the basis of the MDU findings in 26 out of 90 (28.8%) cases. In middle cerebral artery (MCA) aneurysms, the MDU results were relevant to the surgical procedure in 17 out of 44 (38.6%) cases. Whereas with aneurysms of the anterior cerebral artery significant findings occurred in only five of 32cases (15.6%; p<0.05). The clip was repositioned on the basis of the MDU results in 18 out of 50 (36%) aneurysms in patients with subarachnoid haemorrhage (SAH) grade I-V compared with only eight out of 40 (20%) aneurysms in patients without SAH (p<0.05). CONCLUSIONS MDU should be used routinely in cerebral aneurysm surgery, especially in cases of MCA aneurysms and after SAH. Present data show that a postoperative angiography becomes superfluous whenever there is good visualisation of the “working site” and MDU findings are clear.

Clinical evaluation of a new intracranial pressure monitoring device.

Summary. Background: Continuous monitoring of intracranial pressure (ICP) still plays a key role in the management of patients at risk from intracranial hypertension. Numerous ICP-measuring devices are available. The aim of the present study was to investigate the clinical characteristics and the magnetic resonance imaging (MRI) compatibility of the recently developed Neurovent-P® (REHAU AG+CO, REHAU, Germany) ICP monitoring device. Method: In a prospective two-center study, a total of 98 patients with severe head injury, subarachnoid haemorrhage, intracerebral haemorrhage, and non-traumatic brain edema underwent intraparenchymal monitoring of ICP using the Neurovent-P®. A control group comprising 50 patients underwent implantation of the Camino®-OLM-110-4B ICP monitor. The zero drift of the probes was determined before and after the ICP recording period. Technical and medical complications were documented. The MRI compatibility of the Neurovent-P® ICP probe was investigated by evaluating artifacts caused by the probe, probe function and temperature changes during MRI, and probe movement caused by the magnetic field. Findings: The mean zero drift was 0.2±0.41 mmHg (maximum 3 mmHg) for the Neurovent-P® ICP probes and 0.4±0.57 mmHg (maximum 12 mmHg) for the Camino®-OLM-110-4B ICP probes. No significant correlation was identified between the extent of zero drift following the removal of the probes and the length of monitoring. Intraparenchymal haemorrhage spatially related to the probe occurred in 1 out of 50 (2%) patients with a Camino®-OLM-110-4B probe and in 1 out of 98 (1%) with a Neurovent-P®. Damage of the probe due to kinking or overextension of the cable or glass fiber occurred in 4 of the 50 (8%) Camino®-OLM-110-4B ICP probes and in 5 of the 98 (5%) Neurovent-P® probes. On T2-weighted MR images, the Neurovent-P® ICP probe induced only small artifacts with very good discrimination of the surrounding tissue. On T1-weighted MR images, there was a good imaging quality but artifact-related local disturbances in signal occurred. There was no temperature change in the Neurovent-P® probe and in the surrounding brain tissue during MR imaging. Interpretation: The Neurovent-P® ICP measuring system is a safe and reliable tool for ICP monitoring. Handling of the Neurovent-P® system is safe when performed properly.

Surgical treatment of spinal hemangioblastomas.

Summary Background. The routine use of magnetic resonance imaging (MRI) in recent years for the diagnostic assessment of the spinal column and especially for screening patients with von Hippel-Lindau (vHL) disease has shown that spinal hemangioblastomas (sHBs) are more common than assumed so far. Since most sHBs are thus discovered while they are still asymptomatic, especially in vHL disease, the question arises whether and when these tumors should be treated. The present article reports the results of the surgical treatment of sHBs using the protocol described below and compares them to the course in a control group of patients with conservatively treated sHBs. Patients and Methods. A total of 30 sHBs were treated microsurgically in 15 patients. Hemangioblastoma-associated cysts were merely opened in 14 cases, drained with the help of Teflon cotton in 2 of these cases, and not opened in 4 instances. Laminoplasties were performed with insertion of absorbable, MRI-compatible micro-osteosynthesis plates. Perioperatively, all patients were administered methylprednisolone according to the NASCIS (National Acute Spinal Cord Injury Study) scheme, and sensory evoked potentials were monitored intra-operatively in all cases. Nine patients in whom the course of primarily conservative treatment of a total of 17 asymptomatic sHBs was documented served as controls. The follow-up time was 7 to 51 months (mean 20) after surgery and 10 to 51 months (mean 21) in the control group. Findings. Preoperative HB-associated pareses showed transient postoperative deterioration (n=5). The other accompanying neurological deficits improved in 6 HBs and remained unchanged in all other HBs (n=19), of which 16 had been asymptomatic before surgery. In the control group, 6 HBs (in 6 different patients) became permanently symptomatic despite subsequent surgical treatment according to the study protocol. Interpretations. With the new diagnostic tools now available, microsurgical removal of spinal hemangioblastomas has a low morbidity rate, suggesting that surgical treatment should be considered even for asymptomatic sHBs in certain circumstances.

Animal model for cerebral arteriovenous malformation.

Summary Background. The present study was conducted to establish an animal model for the investigation of the pathophysiology and haemodynamics of cerebral arteriovenous malformation (AVM) but also to assess therapeutic aspects. Method. For anatomic and haemodynamic reasons, dogs were chosen as the animal model. An arteriovenous fistula was created by interposing a segment of the superficial temporal artery between one of the main branches of the middle cerebral artery and the dorsal sagittal sinus. A temporal muscle graft supplied by this artery was implanted intracerebrally in the ischaemic area. Findings. The angiographic and histopathologic findings obtained in the animal model are comparable with the situation found in intracerebral AVM in humans. Interpretation. The animal model of intracerebral AVM established in this study allows for further investigation of the pathophysiology and dynamics of this disorder. It may help to develop better therapeutic options and thus improve the prognosis of affected patients.

The Value of Intraoperative Angiography for Surgical Treatment of Cerebral Arteriovenous Malformations in Eloquent Brain Areas

Summary Intraoperative digital subtraction angiography (DSA) allows intraoperative assessment of outcome of cerebral arteriovenous malformations (AVM). This study reports on 21 patients with AVMs in eloquent areas of the brain extirpated between July 1995 to March 1998. Extirpation was always followed by intraoperative DSA. Intraoperative angiography disclosed an occult residual nidus in 4 cases (19%). Complete extirpation of the AVM was achieved in all cases. Following surgery the neurological condition improved in 15 cases (71%), remained unchanged in 5 (24%), and worsened in 1. There were no secondary postoperative haemorrhages, nor complications related to the angiography. These results indicate that intraoperative DSA should be considered in the course of surgical treatment of cerebral AVMs in eloquent areas of the brain.

Brain tumor surgery in geriatric patients: a critical analysis in 44 patients over 80 years.

BACKGROUND The decision of whether to operate on brain tumors in elderly patients has not been made easier despite diagnostic and therapeutic advances facilitating their diagnosis. Little is known about the outcome of brain tumor surgery in patients 80 years or older probably because the number of these patients, although increasing, is still small. METHODS The results of brain tumor surgery in 44 patients aged 80-86 years (mean age 83 years) were analyzed to determine which factors are relevant in the evaluation of the operative risk. The following parameters were analyzed with regard to the outcome: tumor volume, location, histopathology, preoperative condition, and concomitant diseases. RESULTS At discharge 19 patients (43%) had improved while 14 (32%) remained unchanged. Nevertheless, the overall results were unsatisfactory in 10 patients (23%), of whom 5 died in hospital. Tumor location, volume, and histopathology did not correlate with the outcome. The preoperative cerebrovascular condition and the existence of multiple concomitant diseases were clearly the determining factors for the outcome. CONCLUSIONS These results indicate that patients with life-threatening tumors or those causing persistent and intolerable brain dysfunction suffering from symptomatic cerebrovascular atherosclerosis as well as from multiple treatment requiring concomitant diseases did definitely not benefit from surgery.

Biodegradable implants in neurosurgery.

Summary Background. Biodegradable materials have been used for osteosynthesis by orthopedic surgeons and craniomaxillofacial surgeons for many years. However, such materials are not yet widely used by neurosurgeons despite potential applications. This prospective study was undertaken to evaluate potential applications of biodegradable materials in neurosurgical interventions. Methods. A total of 104 4-hole plates and 228 screws consisting of copolymer of poly-70 L/30 D,L-lactide were inserted for fixation of bone flaps in 8 patients and for reinsertion of laminoplasties at 28 levels in 16. The craniotomies were performed for removal of a brain tumour in 4 cases, for surgical management of an aneurysm or cerebral AVM in 2, and for treatment of craniocerebral trauma in another 2. Laminoplasties were performed at 25 levels for intraspinal hemangioblastomas in 15 patients. One patient with an ependymoma underwent 3-level laminoplasty. Findings. One patient with severe head injury in whom the bone flap was re-implanted several months following the craniectomy, developed an aseptic necrosis of the bone flap, which had to be removed. Implant rejection was not observed. One patient suffered from mild local pain in the area of a biodegradeable screw in the frontal region following removal of a sphenoid wing meningeoma. None of the patients with laminoplasty showed signs of functional instability or spinal cord compression. Implant rejection was not observed. No delayed healing or infection occurred. Healing was not delayed and no infections occurred. Interpretation. The results encourage further use of biodegradable materials for the described applications. Additional studies will be performed to investigate the usefulness of biodegradable devices in neurosurgery and to obtain long-term results.

Demonstration of Cerebral Plasticity by Intra-Operative Neurophysiological Monitoring: Report of an Uncommon Case

Summary It has been postulated long ago that “eloquent” areas shift their location in patients with arteriovenous malformations (AVM). Obviously the “motor region” in not located in the precentral gyrus in a patient with an AVM in the “motor region”. We report on the case of a 15-year old boy with an AVM in the left sensorimotor cortex, in whom intra-operative mapping showed an inexcitability of the precentral gyrus, while stimulation of the cortex anterior to the primary motor cortex elicited motor responses. This indicates that motor function was translocated from the primary to the supplementary motor cortex. Surgery was performed under general anaesthesia. Neurophysiological monitoring was performed throughout surgery. The central sulcus was identified by phase reversal of the somatosensory evoked potentials. The motor cortex was mapped by direct high-frequency (500 Hz) monopolar anodal stimulation. In the patient herein reported, stimulation of the “anatomically” defined primary motor cortex induced no motor response, as expected. Motor response was elicited only by stimulation of the cortex anterior to the precentral gyrus. There was no postoperative deterioration of motor function. These observations indicate that the precentral gyrus was functionally “useless”. The motor region was relocated into more rostral areas in the supplementary motor cortex. This translocation of function in the presence of an AVM indicates cerebral plasticity.

Spontaneous bilateral chronic subdural haematoma of the posterior fossa. Case report and review of the literature.

Summary.Summary. Introduction: Chronic subdural haematomas of the posterior fossa in adults without a history of trauma are very rare. To our knowledge, only 15 cases have so far been reported in the literature, including those with anticoagulation therapy. A case of spontaneous bilateral infratentorial chronic subdural haematoma associated with anticoagulation therapy in an alive adult is presented and the relevant literature is reviewed. Case Report: A 70 year old female presented with progressive dizziness, vertigo and gait ataxia. She was on anticoagulation therapy for heart disease. Neuro-imaging revealed bilateral infratentorial subdural masses. The subdural masses were suspects for chronic subdural haematomas by neuroradiological criteria. Because of the progressive symptomatology, the haematomas were emptied through burrhole trepanations. Chocolate-colored fluid, not containing clotted components, gushed out under great pressure. The source of bleeding could not be identified. The patient recovered well from surgery, but died 4 months later shortly after admission to another hospital from heart failure. Discussion: The chronic subdural haematomas in this patient may have been due to rupture of bridging veins caused by a very mild trauma not noticed by the patient and possibly aggravated by the anticoagulation therapy. Infratentorial chronic subdural haematoma should at least be a part of the differential diagnosis in elderly patients with cerebellar and vestibular symptomatology even without a history of trauma.