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Timothy C Ryken

Publications and source records attributed to Timothy C Ryken.

23 records · Page 2Linked to original sources
PubMed2002

Apoptosis and survival in high-grade astrocytomas as related to tumor Fas (APO-1/CD95) expression.

Although a majority of high-grade gliomas express the apoptosis-inducing receptor Fas, little is known about the extent of apoptosis or prognostic significance of Fas expression in these tumors. In situ labeling of apoptotic cells and Ki-67 immunohistochemistry were performed on 51 high-grade human astrocytomas previously characterized for Fas expression. Survival data was compiled from patient records and correlated with tumor grade, apoptotic index (AI) and Fas expression. A significant correlation was found between tumor grade and the AI and Ki-67 labeling index (LI); however, only the AI increased significantly with Fas expression. The AI increased from 0.39 +/- 0.12% to 0.82 +/- 0.10% in grade III vs. IV astrocytomas (P = 0.003). The Ki-67-LI increased from 3.64 +/- 1.5% to 11.35 +/- 2.1% in grade III vs. IV astrocytomas (P = 0.004). Additionally, tumors expressing higher Fas levels had a greater AI than those expressing lower levels (0.81 +/- 0.11% vs. 0.43 +/- 0.11%) (P = 0.017). Despite longer median survivals for patients with tumors exhibiting high Fas expression, statistical significance was not achieved. Patients with grade III astrocytomas demonstrated a median survival of 20 vs. 18 months for tumors with high vs. low Fas expression (P = 0.51). Patients with grade IV astrocytomas demonstrated a median survival of 9 vs. 7.4 months for tumors with high vs. low Fas expression, respectively (P = 0.77). Although the degree of Fas expression in high-grade astrocytomas appears to correlate with the apoptotic rate, no overall differences in survival could be demonstrated between tumors expressing high vs. low Fas levels.

Adult↗
PubMed2002

Enhanced anatomic visualization with ultrasound-assisted intracranial image-guidance in neurosurgery.

Anatomical comparisons between ultrasound images and magnetic resonance imaging (MRI)/computed tomography (CT) preoperative images were performed in four ultrasound-assisted image-guided intracranial surgeries. An ultrasound scanner connected to a surgical navigation system allowed the neurosurgeon to acquire useful views from that integration, offering an improved method for visualization. This surgical navigation device and associated ultrasound provides real-time brain shift correction. The accuracy of navigation depends on the identification of the anatomic structures. Despite some limitations of the ultrasound images, the ability to compare preoperative MRI and intraoperative ultrasound proved useful to the surgeon.

Aged↗
PubMed2002

Modification of reference array attachment for image guided neurosurgery: direct cranial fixation.

We have modified the cranial fixation technique of the reference array used for the Stealth (Medtronics Inc., Minneapolis, MN) image guided neurosurgical workstation to avoid rigid immobilization and to accommodate patients undergoing awake procedures. The modification allows attachment of a reference array directly to the skull prior to registration, avoiding the requirement for rigid cranial fixation. The accuracy of fiducial registration for the modified reference array was compared to the conventional reference array using a phantom system yielding similar registration results and target accuracy. The successful application of the modified system to two operative cases is described.

Aged↗
PubMed1999

Instability of the craniovertebral junction and treatment outcomes in patients with Down's syndrome.

Operative intervention for the treatment of instability at the craniovertebral junction in patients with Down's syndrome has become somewhat controversial because some authors have reported high surgery-related complication rates and suggested that the incidence of neurological abnormality associated with this abnormal motion may be low. In this report, the authors describe the clinical and radiographic findings in 33 patients treated at their institution. Common presenting symptoms included neck pain (14 patients), torticollis (12 patients), and myelopathy manifested as hyperreflexia (21 patients), or varying degrees of quadriparesis (11 patients). Four patients suffered acute neurological insults, two after receiving routine general anesthetics for minor surgical procedures and two other patients following minor falls. Atlantoaxial instability was the most common abnormality documented on radiography (22 patients). Atlantooccipital instability (15 patients) was also frequently observed and was coexistent with the presence of atlantoaxial luxations in 14 patients. A rotary component of the atlantoaxial luxation was present in 13 cases. In 17 patients bony anomalies were present, the most frequent of which was os odontoideum (10 patients). Twenty-four patients underwent operative intervention, and successful fusion was achieved in 23. In six of nine patients with basilar invagination, reduction was achieved with preoperative traction and thus avoided the need for ventral decompressive procedures. There were no cases of postoperative deterioration, and 22 patients made excellent or good recoveries. The results of this series highlight the clinicopathological phenomena of craniovertebral instability in patients with Down's syndrome and suggest that satisfactory outcomes can be achieved with a low rate of surgical morbidity.

Journal Article↗