Selçuk Peker

First intraoperative, shared-resource, ultrahigh-field 3-Tesla magnetic resonance imaging system and its application in low-grade glioma resection

OBJECT The authors describe the first shared-resource, 3-T intraoperative MR (ioMR) imaging system and analyze its impact on low-grade glioma (LGG) resection with an emphasis on the use of intraoperative proton MR spectroscopy. METHODS The Acibadem University ioMR imaging facility houses a 3-T Siemens Trio system and consists of interconnected but independent MR imaging and surgical suites. Neurosurgery is performed using regular ferromagnetic equipment, and a patient can be transferred to the ioMR imaging system within 1.5 minutes by using a floating table. The ioMR imaging protocol takes < 10 minutes including the transfer, and the authors obtain very high-resolution T2-weighted MR images without the use of intravenous contrast. Functional sequences are performed when needed. A new 5-pin headrest-head coil combination and floating transfer table were specifically designed for this system. RESULTS Since the facility became operational in June 2004, 56 LGG resections have been performed using ioMR imaging, and > 19,000 outpatient MR imaging procedures have been conducted. First-look MR imaging studies led to further resection attempts in 37.5% of cases as well as a 32.3% increase in the number of gross-total resections. Intraoperative ultrasonography detected 16% of the tumor remnants. Intraoperative proton MR spectroscopy and diffusion weighted MR imaging were used to differentiate residual tumor tissue from peritumoral parenchymal changes. Functional and diffusion tensor MR imaging sequences were used both pre- and postoperatively but not intraoperatively. No infections or other procedure-related complications were encountered. CONCLUSIONS This novel, shared-resource, ultrahigh-field, 3-T ioMR imaging system is a cost-effective means of affording a highly capable ioMR imaging system and increases the efficiency of LGG resections.

Radiosurgical treatment of cavernous sinus cavernous haemangiomas.

SummaryBackground. The objective of this report is to evaluate the effects of radiosurgery on cavernous sinus cavernous haemangiomas (CSCHs). Method. Five cases of CSCHs are presented in this report. One of them was diagnosed only neuroradiologically. Other patients underwent surgery and were then referred to Gamma Knife radiosurgery for residual tumours. The cohort consisted of 3 male and 2 female patients with median age of 42 (37–60). The volume of the tumours ranged between 3.8–6.5 cc. They were treated with a marginal dose of 14 to 16 Gy (mean 15 Gy). Findings. In the mean follow-up period of 32 months (6–52 months) all of the tumours decreased in size. There were no complications related to radiosurgery. Conclusion. Gamma Knife radiosurgery is an effective method in the treatment of CSCH, over the period of follow-up described.

Superficial siderosis due to papillary glioneuronal tumor

Superficial siderosis of the central nervous system is a rare, progressive, irreversible and debilitating neurological disease characterized by the deposition of haemosiderin in the leptomeninges and the subpial layers of the brain and spinal cord. The main clinical findings are progressive bilateral sensorineural hearing loss, cerebellar ataxia and pyramidal tract signs. The present report describes a 49-year-old woman who presented with intermittent headache of 5 years duration. The pain had become more severe in the previous 6 months. Neurological examination revealed nothing abnormal. Computed tomography showed a cystic mass with apparent internal haemorrhage in the right frontal lobe and T(2)-weighted magnetic resonance imaging showed material of low signal intensity coating the entire surface of the brain. The mass was completely excised via craniotomy. A histopathological study identified the mass as a papillary glioneuronal tumour. The patient recovered well and is still neurologically normal 1 year later. This is the first documented case of superficial siderosis caused by this type of tumour.

Microsurgical anatomy of the lateral walls of the pituitary fossa

SummaryBackground. The aim was to evaluate the microanatomy of the lateral wall of the pituitary fossa in cadavers.Methods. Histological sections of sellar-parasellar specimens from 13 cadaver heads were examined. The thickness of the pituitary capsule and inferior and lateral walls of the pituitary fossa were measured, and the collagenous structure of these layers was evaluated.Findings. The pituitary gland is enveloped by a tough, thin, fibrous capsule. The inferior wall of the pituitary fossa is composed of relatively thick dura (mean thickness in the 13 specimens, 171 µm). Each lateral wall of the fossa has a thin layer of dura (mean thickness in the specimens, 85 µm). The pituitary capsule and the dural layers in the lateral and inferior walls of the fossa were immunopositive for collagen types I and II. Collagen types III, IV and V were detected only in the pituitary capsule.Conclusions. Weakness of the lateral walls of the pituitary fossa and the degree to which collagen fibres in the pituitary capsule have been biochemically damaged are important factors in infiltration of the cavernous sinus by a pituitary adenoma.

Gamma-knife radiosurgery in the treatment of trigeminal schwannomas

SummaryBackground. Trigeminal nerve schwannomas account for 0.07%–0.28% of all intracranial tumours. Advances in skull base surgery have led to more aggressive resection of these tumours, but surgery may associated with development of new neurological deficits. Methods. In this report, we analyse the long-term results 15 patients with newly diagnosed or residual/recurrent trigeminal schwannoma who underwent gamma-knife treatment. Findings. During a mean 61 months of follow-up, MRI revealed reduction of tumour size in 13 and no size change in 2 patients. The tumour growth control rate was 100% and only 1 patient had transient facial numbness and diplopia. Conclusions. For patients with small to moderate size trigeminal schwannomas, gamma-knife radiosurgery is associated with good tumour control and a minimal risk of adverse radiation effects.

Surgical treatment of intramedullary spinal cord ependymomas: Can outcome be predicted by tumor parameters?

Objective: The aim of this study was to investigate whether the tumor parameters of spinal intramedullary ependymomas are significant predictors of clinical presentation and postsurgical outcome. Methods: The study involved 21 cases of intramedullary ependymoma that were operated on between 1988 and 2001. The patients were 13 males (62%) and 8 females (38%), with an age range of 9-70 years (median 38 years). Results: In most cases (13; 62%), preoperative neurologic examination revealed a sensorimotor deficit in at least one limb. Complete tumor removal was achieved in all cases. The patients with wider tumors had poorer preoperative neurologic condition and poorer neurologic outcome. Tumor length (equivalent to myelotomy length) was not correlated with preoperative neurologic status, but longer length was significantly associated with development of dysesthesia post surgery. In contrast to tumor length, tumor/cord ratio (ratio of the tumor width to the largest cord width at the tumor site) was identified as a significant predictor of preoperative neurologic status and outcome. Ratio values of >0.80 were correlated with poorer preoperative clinical status and poorer neurologic outcome. Neither extent of edema (determined from length [in millimeters] of hyperintensity on T2-weighted images) nor presence of a cyst in the tumor was significant relative to postoperative neurologic recovery in these cases. Conclusions: This study demonstrated that the width of the tumor relative to the cord is the main predictor of neurologic presentation and postoperative status. The length of the tumor affects the postoperative dysesthesia development.

Irradiation After Surgically Induced Brain Injury in the Rat: Timing in Relation to Severity of Radiation Damage

The aim of this study was to evaluate how timing of irradiation after brain surgery in rats relates to overall extent of brain radiation damage. Extent of injury was determined according to lipid peroxidation (malondialdehyde; MDA) levels in brain tissue. Thirty female rats were randomly assigned to five equal groups (Groups A–E). Four groups underwent trephination and scalpel hemisection of right frontal lobe. Rats in Groups B and D received 25 Gy cranial irradiation in a LINAC system at 10 and 20 days after surgery, respectively. Twenty-four hours later they were killed and their right frontal lobes were removed for lipid peroxidation determination. Groups A and C were not irradiated; these groups were killed and had their frontal lobes removed on day 11 and day 21 post-surgery, respectively. The remaining six animals (Group E, sham surgery) underwent trephination only, and were killed and had their frontal lobes removed 24 h later.There was a significant difference between the mean MDA levels in the control group and Group D, and between the levels in Group B and Group D (P < 0.05 for both). The difference between the mean for Group A and the mean for Group B was even more significant (P < 0.01). The most striking differenceswere between the control group and Group B, and between Group B and Group C (P < 0.001 for both).The data from this rat model suggest that, in humans, starting radiotherapy early (1–2 weeks) after debulking of a brain tumor may result in significantly higher levels of tissue damage than if the radiation is started 3 weeks or more postoperatively. Further experimental research is needed to project these findings in rats to human subjects.

Critical appraisal of RapidArc radiosurgery with flattening filter free photon beams for benign brain lesions in comparison to GammaKnife: a treatment planning study.

BackgroundTo evaluate the role of RapidArc (RA) for stereotactic radiosurgery (SRS) of benign brain lesions in comparison to GammaKnife (GK) based technique.MethodsTwelve patients with vestibular schwannoma (VS, n = 6) or cavernous sinus meningioma (CSM, n = 6) were planned for both SRS using volumetric modulated arc therapy (VMAT) by RA. 104 MV flattening filter free photon beams with a maximum dose rate of 2400 MU/min were selected. Data were compared against plans optimised for GK. A single dose of 12.5 Gy was prescribed. The primary objective was to assess treatment plan quality. Secondary aim was to appraise treatment efficiency.ResultsFor VS, comparing best GK vs. RA plans, homogeneity was 51.7 ± 3.5 vs. 6.4 ± 1.5%; Paddick conformity Index (PCI) resulted 0.81 ± 0.03 vs. 0.84 ± 0.04. Gradient index (PGI) was 2.7 ± 0.2 vs. 3.8 ± 0.6. Mean target dose was 17.1 ± 0.9 vs. 12.9 ± 0.1 Gy. For the brain stem, D1cm3 was 5.1 ± 2.0 Gy vs 4.8 ± 1.6 Gy. For the ipsilateral cochlea, D0.1cm3 was 1.7 ± 1.0 Gy vs. 1.8 ± 0.5 Gy. For CSM, homogeneity was 52.3 ± 2.4 vs. 12.4 ± 0.6; PCI: 0.86 ± 0.05 vs. 0.88 ± 0.05; PGI: 2.6 ± 0.1 vs. 3.8 ± 0.5; D1cm3 to brain stem was 5.4 ± 2.8 Gy vs. 5.2 ± 2.8 Gy; D0.1cm3 to ipsi-lateral optic nerve was 4.2 ± 2.1 vs. 2.1 ± 1.5 Gy; D0.1cm3 to optic chiasm was 5.9 ± 3.1 vs. 4.5 ± 2.1 Gy. Treatment time was 53.7 ± 5.8 (64.9 ± 24.3) minutes for GK and 4.8 ± 1.3 (5.0 ± 0.7) minutes for RA for schwannomas (meningiomas).ConclusionsSRS with RA and FFF beams revealed to be adequate and comparable to GK in terms of target coverage, homogeneity, organs at risk sparing with some gain in terms of treatment efficiency.

Giant pericallosal artery aneurysm: case report and review of the literature

Abstract  Pericallosal artery aneurysms comprise 5% of all intracranial saccular aneurysms and are usually small. Giant cerebral aneurysms mostly occur in major arteries. To date, 12 cases of giant pericallosal artery aneurysm have been reported in the literature. An unusual giant thrombosed pericallosal artery aneurysm is reported here. A 65-year-old female presented with headache and personality changes. Computed tomography, magnetic resonance imaging, and cerebral angiography revealed a right-sided giant thrombosed pericallosal artery aneurysm. The patient was operated via an anterior interhemispheric approach and the neck of the aneurysm was successfully clipped. The postoperative period was uneventful. This rare lesion is one of few cases presented in the literature in which neuroradiologic and neuropathologic evaluation was completely performed and the neck of the aneurysm was clipped.

Solid-calcified colloid cyst of the third ventricle

We report a 65-year-old female with a solid-calcified colloid cyst in the third ventricle that was demonstrated on computed tomography scan and magnetic resonance images. The lesion was surgically excised using the anterior transcallosal-transforaminal approach. Complete preservation of the surrounding neural and vascular structures was achieved.