Biomedical subjects
Publications and source records attributed to K Ashkan.
Anatomical variations of neural structures in the cervical spine are rare and are not necessarily visible on pre-operative imaging. The authors report an unusual arrangement of neural structures identified during cervical foraminotomy. Anatomical variations of the cervical nerve roots are reviewed and their importance in neurosurgical practice is discussed.
Since its advent in 1993, high frequency stimulation (HFS) of the subthalamic nucleus (STN) has rapidly developed into the most commonly practiced surgical procedure for the treatment of Parkinson's Disease (PD). Although its exact mechanism of action, be it through an inhibitory depolarization block, desynchronization of neuronal circuits or other means, is not clear, the efficacy and safety of the technique are now well established. HFS of the STN improves the motor function by at least 60%, drastically reduces the levodopa requirement and significantly improves the quality of life in PD. This review updates the recent concepts on the pathophysiology of PD and analyses the basic science principles underlying the clinical practice of the STN HFS. The evolution of the surgical technique and long-term patients' outcome are further discussed.
A case of meningeal melanocytoma in the posterior fossa of a 16-year-old male is reported. Computed tomographic and magnetic resonance imaging features are presented. Pathological investigation including light and electron microscopy, and immunohistochemical staining are discussed. Current literature is reviewed and differentiating criteria from meningioma and other pigmented tumours of the nervous system are discussed.
Neurophysiological studies (NPS) are often used by both neurosurgeons and neurologists to supplement neuroimaging findings in the diagnosis of cervical radiculopathy and in operative decision-making. The aim of this study was to assess whether nerve conduction and electromyographic studies added significant information to that obtained from high resolution MRI to warrant routine use. Over the 10-year period (1991-2001), we identified 48 patients who underwent both preoperative NPS and MRI for cervical radiculopathy. Sensitivity of MRI and NPS for diagnosing cervical radiculopathy was 93 and 42%, respectively. Whilst the positive predictive values for MRI and NPS were similar (91% versus 86%), the former had a higher negative predictive value (25% versus 7%). In only one case was the decision to operate based on NPS despite a negative MRI. We therefore suggest that in patients with clinical and MRI evidence of cervical radiculopathy, NPS has limited additional diagnostic value.
A patient with an unusual cystic meningioma is described. The pathophysiology of cyst formation is discussed.
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We report two young patients with obscure presentations of gliomatosis cerebri. Initial CT scanning was inconclusive and in one case showed intraventricular haemorrhage, a feature not previously described. Magnetic resonance imaging was required to show the lesions with greater definition; however, in both cases, a biopsy was needed to confirm the diagnosis.
In the light of the recent recommendations of the Society of British Neurological Surgeons on safe neurosurgery, we prospectively audited the work load, availability and efficiency in the use of neurosurgical resources in our department over a 1-month period. There were a total of 130 admissions--70 emergency and 60 elective cases. Twenty-three patients referred as emergencies were denied admission, directly or indirectly, because of shortage of beds. Other emergency cases had to wait unacceptable long periods, up to 17 days, prior to admission for the same reason. For elective cases, there was a 33% cancellation rate due to lack of beds and competition with the emergency cases for the same resources. Overall bed occupancy rate exceeded 100%. We conclude that the current neurosurgical resources are inadequate and over-stretched leaving no safety margin. Neurosurgery as a core emergency service, therefore, should be given priority in NHS resource allocation.
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BACKGROUND: "Central neurocytoma" is classically considered as an intraventricular benign tumor, largely based on data from small retrospective series. The authors present prospective data on 12 patients with tumors diagnosed as central neurocytoma, to highlight the diverse nature of this tumor and challenge the classic notion. METHODS: Between 1991 and 1997, 12 patients had tumors diagnosed prospectively as "central neurocytoma". Clinical, radiologic, and histologic data were collected, and Karnofsky performance score was evaluated for each patient. Proliferation marker studies were performed using Ki-67 labeling index. RESULTS: In two patients, the tumors were located in atypical locations, namely, the parietal lobe and the spine. Aggressive behavior characterized by clinical and radiologic evidence of tumor progression was noted in two additional patients. In both these cases, unusually high proliferation rates of 5.3% and 11.2% were noted. Total excision of the tumor, when possible, was the treatment of choice. Postoperative radiotherapy to the residual tumor may be of benefit in patients with clinically aggressive tumors, or those with high proliferation rates. CONCLUSIONS: Given the findings of this study, it is suggested that the traditional concept of central neurocytoma as a benign intraventricular tumor warrants reconsideration.
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The availability of magnetic resonance imaging has greatly increased the detection of cavernous malformations of the central nervous system in both symptomatic and asymptomatic patients. These lesions may be responsible for previously unexplained neurological events or may even have been incorrectly diagnosed. We describe a patient presenting with focal neurological signs in whom an initial diagnosis of malignant glioma had been made. Following excision, the pathological diagnosis was cavernoma. This vascular lesion has continued to show rapid growth and aggressive behaviour despite multiple surgical resections. The indications for operative and non-operative intervention will be discussed.
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A dislocated pisiform associated with type II Salter-Harris fractures of the distal radius and ulna in a 9-year-old child is described. Closed reduction followed by immobilization achieved good radiological and clinical results. The current literature on dislocation of the pisiform is reviewed.
Four cases of intracranial osteosarcoma are reported. In three cases the tumors were primary neoplasms arising from the sellar region, base of the occiput and the parieto-occipital area. One case represented osteosarcoma metastatic to the cerebellum, a site not previously described, from a primary tumor at the femur. In addition, the current literature on intracranial osteosarcoma is reviewed.