Biomedical subjects
Michael Vassilyadi
Publications and source records attributed to Michael Vassilyadi.
Atypical teratoid/rhabdoid tumors.
CASE REPORTS: We describe three cases of atypical ATRT that were identified at the Children's Hospital of Eastern Ontario. DISCUSSION: Over the past decade, atypical teratoid/rhabdoid tumors (ATRTs) of the central nervous system have emerged as a distinct entity. This tumor is typically misdiagnosed as a primitive neuroectodermal tumor (PNET)/medulloblastoma. The unique immunohistochemistry profile of an ATRT helps distinguish it from a PNET/medulloblastoma. This is of clinical importance because the prognosis of a patient with an ATRT is worse than that of a PNET/medulloblastoma despite aggressive surgical treatment with or without adjuvant chemotherapy and radiation therapy.
The role of cine flow MRI in children with Chiari I malformation.
INTRODUCTION: Since the introduction of MRI, the incidence of Chiari I malformations (cerebellar tonsils ectopia) has increased. The clinical significance of this finding remains questionable in some instances. Recently, cine flow MRI has added to the understanding of the dynamics of cerebrospinal fluid at the craniocervical junction and to the pathophysiology of the Chiari I malformation. The present study attempts to analyze the role of cine flow MRI in Chiari I malformations. MATERIALS AND METHODS: Between January 1990 and December 2000, 24 patients were identified who met the following inclusion criteria: patients diagnosed with Chiari I malformation who had had an MRI of the brain including the craniocervical junction, clinical follow-up for at least six months, and cine flow studies had to have been performed pre- and postoperatively. The cine flow studies were repeated during follow-up if the patients were not surgical candidates. Patients harboring intracranial space occupying lesions or lumboperitoneal shunts were excluded. Sixteen of the 24 selected patients underwent 18 operations and 8 were followed conservatively. There was a wide variation in clinical presentations. Twelve patients had cerebellar tonsils protruding more than 5 mm below the foramen magnum, and in 12 patients the descent of the cerebellar tonsils was less than 5 mm. Despite this difference in the degree of protrusion, there was no significant difference in clinical presentation. The cisterna magna was small or absent in 20 patients with sluggish cine flow posteriorly, 19 of whom were symptomatic, in contrast to 1 symptomatic patient who had satisfactory cine flow. RESULTS: All patients with Chiari I malformation and an associated cervical syrinx had absent cine flow at the craniovertebral junction, and this finding was statistically significant. There was a good correlation between the clinical presentation and cine flow preoperatively, and between clinical improvement and cine flow postoperatively. Patients with Chiari I malformation, cervical syrinx, and absent cine flow preoperatively improved after suboccipital decompression and duroplasty. Patients with Chiari I malformations without syrinx and absent cine flow underwent suboccipital bony decompression alone and had satisfactory outcomes.
Cognitive sequelae in children with posterior fossa tumors.
Late effects of radiotherapy on intellectual functioning have been well documented in children treated for posterior fossa tumors. Other aspects of cognitive functioning, such as memory, have not been adequately assessed in this population. This retrospective review reports on 15 children diagnosed with medulloblastoma or cerebellar astrocytoma who were administered a norm-referenced standardized test of memory functioning (i.e., Wide Range Assessment of Memory and Learning) an average of 3.5 years after treatment. Analyses revealed that sample means of IQ and memory were significantly lower than those of the normative population. No significant differences were found between the verbal and nonverbal IQ, or verbal and visual memory. Age at diagnosis accounted for a significant proportion of variability in the intelligence ratings but not in the memory indexes. The IQ scores of children less than 6 years of age at diagnosis were significantly lower than those of children diagnosed when over 6 years of age. Given the substantial variability within the older age group, there was insufficient power to detect true differences between memory index means for children by age at diagnosis. Follow-up assessments over 5 years may better identify the long-term effects of radiotherapy on memory functioning.
Late-onset erythema along a sterile functioning ventriculoperitoneal shunt: case report and review of the literature.
CASE REPORT: A 6-year-old boy presented with erythema along the tract of his ventriculoperitoneal shunt 6 years after its insertion; there was no associated CSF infection or shunt malfunction. DISCUSSION: The question of what to do in such a situation is addressed. The possible causes of the erythema are discussed, as well as its management, and the literature is reviewed.
Neuroendoscopic intracranial pressure monitoring.
OBJECT: We wished to find a way of monitoring patients' intracranial pressure (ICP) during endoscopic surgery. METHODS: The Codman Microsensor ICP monitor can be inserted through the working channel of an endoscope with an interposed assembly (Check Flo II with male fitting, 9 F, manufactured by Cook, model #CFM-100TM) to provide a water-tight seal and allow simultaneous irrigation. During endoscopic third ventriculostomy surgery with this setup in our hospital, the ICP was continuously monitored. The effects of irrigation on ICP were also followed. The sensor was assumed to be absolutely accurate and not referenced to a column of water. CONCLUSION: The small size of the Microsensor ICP monitor enabled easy placement through the working channel of the endoscope and interposed assembly. The ICP reading was continuously available, even during irrigation. The effect of irrigation on ICP was carefully monitored, and limited when pressure changes were noted.