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Biomedical subjects

Peter Kan

Publications and source records attributed to Peter Kan.

At least 19 recordsLinked to original sources
PubMed2006

The role of diffusion-weighted magnetic resonance imaging in pediatric brain tumors.

OBJECTIVES: Diffusion-weighted imaging (DWI) may enhance the radiographic diagnosis of pediatric brain tumors. This study reviews the DWI properties of pediatric brain tumors at our institution and examines their relationship to tumor grade and type. MATERIALS AND METHODS: The preoperative DWI and apparent diffusion coefficient (ADC) characteristics of brain tumors in 41 children were compared with histologic diagnosis. Signal characteristics on DWI and ADC maps correlated well with tumor grade. High-grade lesions were hyperintense on DWI and hypointense on ADC maps. Sensitivity, specificity, positive predictive value, and negative predictive value were 70, 100, 100, and 91%, respectively. Signal characteristics did not differ among different tumors of the same grade. All primitive neuroectodermal tumors showed diffusion restriction whereas none of the ependymomas did. CONCLUSIONS: The signal characteristics on DWI and ADC maps appeared to be strongly correlated to grade in pediatric brain tumors and they may assist with preoperative diagnostic predictions.

Brain Neoplasms↗
PubMed2006

Hybrid imaging using linear retroreflectors.

It has been observed that retroreflective materials can be used in combination with beam splitters to produce real images. This is practical on a large size scale but has a maximum optical efficiency of 25%. Conversely, curved reflectors efficiently produce real images, but their cost increases very rapidly with size. We introduce a new imaging method, which combines the advantages of both systems, through the use of a linear retroreflective film. This material is retroreflective in one plane and conventionally reflective in the perpendicular plane. The net result is an efficient real image system that can have unlimited extent in one transverse direction, and which can be inexpensively manufactured on a large scale.

Journal Article↗
PubMed2006

Cerebrospinal fluid dissecting into spinal epidural space after lumbar puncture causing cauda equina syndrome: review of literature and illustrative case.

OBJECTS: We report a case of epidural cerebrospinal fluid (CSF) leak after lumbar puncture caused by CSF dissecting into the spinal epidural space. The incidence of this phenomenon may be higher than suspected, although most cases may remain asymptomatic. MATERIALS AND METHODS: A 4-year-old girl with new-onset seizure underwent a diagnostic lumbar puncture, the results of which were normal; 3 h later, she began experiencing severe low-pressure headaches and lower back pain, bilateral lower extremity weakness, numbness, and pain, and urinary retention when upright. Spinal MRI demonstrated extensive epidural CSF collection posterior to the thecal sac extending from the cervicothoracic junction to the sacrum. After 48 h in the supine position and gradual mobilization, the patient had complete resolution of symptoms and no neurological sequelae. CONCLUSION: Patients usually recover without any neurological deficits after conservative treatment. Prone or lateral decubitus positioning immediately after lumbar puncture may decrease the incidence of this phenomenon.

Cerebrospinal Fluid↗
PubMed2006

Posterior fossa brain tumors and arterial hypertension.

Hypertension caused by arterial compression of the rostral ventrolateral medulla is well described. Much less information is available on the association between neurogenic hypertension and posterior fossa brain tumors. To date, multiple reports have supported the impression that a small subpopulation of patients with posterior fossa tumors can present with arterial hypertension, and many of those patients achieved significant improvement of their hypertension after tumor resection and medullary decompression. To review the relationship between posterior fossa brain tumors and hypertension, we detail the history, basic science, and clinical reports along with an illustrative case regarding this topic.

Adult↗
PubMed2006

Simple closure following transsphenoidal surgery. Technical note.

The most common nonendocrine complication after transsphenoidal surgery is cerebrospinal fluid (CSF) leak. Many neurosurgeons have advocated the routine reconstruction of the floor of the sella turcica using autologous fat, muscle, fascia, and either cartilage or bone after transsphenoidal surgery to prevent postoperative CSF fistulas. However, the use of autologous grafting requires a second incision, prolongs operative time, and adds to the patient's postoperative discomfort. In addition, the presence of sellar packing may interfere with the interpretation of postoperative images. To avoid these disadvantages, the authors suggest that routine sellar reconstruction or closure after transsphenoidal surgery is unnecessary unless an intraoperative CSF leak is encountered. The incidence of postoperative CSF leakage in the patients reported on in this series is no higher than that reported by others, and no other complications such as pneumatocele have been encountered in approximately 2700 patients in whom no intraoperative CSF leak was encountered. The authors conclude that routine closure of the floor of the sella turcica or sphenoid is unnecessary in the absence of intraoperative CSF leak.

Cerebrospinal Fluid Rhinorrhea↗
PubMed2006

Cervical spine clearance after trauma in children.

OBJECT: Currently, no diagnostic or procedural standards exist for clearing the cervical spine in children after trauma. The purpose of this study was to determine if reeducation of nonneurosurgical personnel and initiation of a new protocol based on the National Emergency X-Radiography Utilization Study criteria could safely increase the number of pediatric cervical spines cleared of suspected injury without a neurosurgical consultation. METHODS: Data regarding cervical spine clearance in children (ages 0-18 years) after trauma protocol activation at Primary Children's Medical Center between 2001 and 2005 were collected and reviewed. Radiographic and clinical methods of clearing the cervical spine as well as the type and management of injuries were determined for two time frames: Period I (January 2001-December 2003) and Period II (January 2004-July 2005). Between 2001 and 2003, 95% of 936 cervical spines were cleared of suspected injury by the neurosurgical service. Twenty-one ligamentous injuries (2.2%) and 12 fracture-dislocations (1.3%) were detected, with five patients requiring surgical stabilization (0.5%). Between January 2004 and July 2005, 507 (68%) of 746 cervical spines were cleared by nonneurosurgical personnel. Six ligamentous injuries (0.8%) and 10 fracture-dislocations (1.3%) were identified, with three patients (0.4%) requiring surgical stabilization. No late injuries were detected in either period. CONCLUSIONS: The protocol used has been effective in enabling detection of cervical spine injuries in children after trauma, with the new protocol increasing by more than 60% the number of cervical spines cleared by nonneurosurgical personnel. Reeducation with establishment of the new protocols can safely facilitate clearance of the cervical spine by nonneurosurgical personnel after trauma.

Cervical Vertebrae↗
PubMed2006

Primary spinal yolk sac tumor with brain metastasis: case report and review of the literature.

OBJECT: Central nervous system primary germ cell tumors are typically pineal or suprasellar. Primary germ cell tumors of the spinal axis are very rare, with only a few case reports of germinomas and teratomas described in the literature. METHODS: We present the unique case of a 25-year-old woman with an intradural, extramedullary primary yolk sac tumor (YST) at and below the level of the conus medullaris. The patient was treated with a subtotal resection and within a month had rapid regrowth of her YST. She was subsequently treated with four cycles of chemotherapy (intravenous cisplatin and etoposide), 40-Gy fractionated focal external beam radiation to the spine, and consolidation with four additional cycles of chemotherapy (intravenous carboplatin, vinblastine, etoposide, and bleomycin). Despite an initial reduction in tumor size and clinical improvement in her neurologic exam, she re-presented a year after surgery with gross enlargement of her spinal tumor and CSF dissemination with metastasis to her brain. Despite further chemotherapy and radiotherapy, the patient died from her disseminated YST. CONCLUSIONS: This case demonstrates that primary YSTs may occur in the spine, and like their intracranial counterparts, are associated with poor prognosis and dissemination through the neuroaxis. When feasible (no evidence of CSF dissemination, metastasis, or multifocal disease), optimal treatment includes as extensive resection of tumor as possible followed by adjuvant chemotherapy and radiation. The authors review the available literature on the treatment of intracranial malignant germ cell tumors, extrapolated to apply to the much rarer spinal lesions.

Adult↗
PubMed2006

Validation of a quality-of-life questionnaire for patients with pituitary adenoma.

BACKGROUND: The purpose of this study was to develop and validate a self-administered questionnaire to measure the health-related quality of life of patients with pituitary adenoma. METHODS: A patient-centred iterative process, involving a literature review and focus group interviews with 84 patients, was used to develop a preliminary 106-item questionnaire and to validate it. The final questionnaire comprised the 30 most important items chosen by 20 patients and 17 items considered important by health care professionals. For assessment of its validity and reliability, 55 patients were asked to complete the final questionnaire, RAND-36, FACT- G/FACT-Br, and Karnofsky Performance Scale (KPS). Concurrent validity of the results of our questionnaire with those of the other instruments was assessed with Pearson correlation coefficients. Known-group validity for the scores of extreme groups was assessed with a Student's t test. Test-retest reliability was determined with Pearson correlation coefficients and a Student's t test for two sets of scores obtained one month apart. RESULTS: Forty-seven (85.5%) of the 55 questionnaires were completed. Our questionnaire was well correlated with the RAND-36, the FACT-Br, the FACT-G, and the KPS in the general health domain, but not with the KPS overall. Extreme groups (n = 20) were significantly different. Test-retest reliability (n = 24) was 0.88, and scores one month apart were not significantly different. CONCLUSION: Our patient-centred health-related quality of life questionnaire developed for patients with pituitary adenoma had good validity and reliability. This questionnaire could be used as a patient-centred outcome measure in clinical trials and for assessment of disease progression.

Adenoma↗
PubMed2006

Cholesteatoma of the clivus.

Cholesteatomas (central nervous system epidermoids) can be found intradurally or extradurally in the central nervous system. Extradural intraosseous lesions are most commonly found in the petrous bone. The authors describe a unique case of a clival cholesteatoma in a 64-year-old woman who presented with headaches. No other neurological complaints or physical examination findings were noted. Magnetic resonance imaging showed an expansile lesion centered in the middle portion of the clivus. A large portion of the clivus was eroded. The lesion was explored via a transnasal trans-sphenoidal approach and granular debris was evacuated. The cystic lining was stripped from the surrounding bone, and the bone opening was widely fenestrated. Pathological examination showed keratinous debris with macrophages and an outer lining of benign epithelial tissue consistent with a cholesteatoma (epidermoid cyst). When surgically accessible, these lesions should be excised to prevent a recurrence. If inaccessible, marsupialization may be considered.

Case Reports↗
PubMed2006

Submandibular-infratemporal interpositional carotid artery bypass for cranial base tumors and giant aneurysms.

OBJECTIVE: Cerebral revascularization is an important strategy in the surgical management of some complex cranial base tumors and unclippable aneurysms. A high-flow bypass may be necessary in planned carotid occlusion or sacrifice. The cervical-to-supraclinoid internal carotid artery bypass or cervical carotid-to-middle cerebral artery bypass are useful procedures to bypass lesions at the base of the cranium. We describe technical modifications of the submandibular-infratemporal interpositional saphenous vein (or radial artery) graft bypass technique specifically designed to avoid removal of the zygoma. METHODS: The saphenous vein or radial artery interpositional graft is tunneled through a burr hole created in the floor of the middle fossa via a submandibular-infratemporal route avoiding removal of zygoma and attachments of the masseter or temporalis muscles. RESULTS: The technique is demonstrated in one patient with removal of a malignant cavernous sinus tumor and in another patient with an unclippable giant carotid bifurcation aneurysm. CONCLUSION: The advantages of this approach include preservation of the facial anatomy and creation of a short and safe route for passage of the saphenous vein or radial artery graft.

Anastomosis, Surgical↗
PubMed2006

Decompression of cavernous sinus meningioma for preservation and improvement of cranial nerve function. Technical note.

Meningiomas are the most common tumors affecting the cavernous sinus (CS). Despite advances in microsurgery and radiosurgery, treatment of CS meningiomas remains difficult and controversial. As in cases of other meningiomas, the goal of treatment for CS meningioma is long-term growth control and preservation of neural function. Gross-total resection, the ideal treatment for meningioma, is not always possible to obtain in patients with CS meningiomas with an acceptable level of morbidity. Therefore, microsurgery and radiosurgery have recently been advocated as a combined therapy to achieve good control of tumor growth and favorable functional outcome. The authors describe a technique in which tumor volume can be reduced to a minimal residual amount, while preserving cranial nerve function. This enables the smallest field to be treated radiosurgically. The optic nerve is decompressed, and the tumor mass is reduced to provide at least a 5-mm interpositional distance between the optic nerve and the residual lesion. Direct decompression of the CS, with opening of the lateral and superior sinus walls, and piecemeal removal of the tumor in "safe" locations are performed to facilitate an improvement in cranial nerve function. The authors describe the use of this technique in a series of patients and demonstrate improvement of cranial nerve function in a subset of these patients.

Adult↗
PubMed2006

Long-term maintenance of cervical alignment after occipitocervical and atlantoaxial screw fixation in young children.

OBJECT: Despite decades of surgical experience, the long-term consequences of occipitocervical (OC) and atlantoaxial (C1-2) fusions in children are unknown. The purpose of this study was to determine the long-term effects of these fusions on growth and alignment of the maturing cervical spine. METHODS: A retrospective chart review was conducted for patients 6 years of age or younger (mean 4.7 years, range 1.7-6.8 years) who underwent OC or C1-2 fusion at the Primary Children's Medical Center at the University of Utah within the last 10 years. Immediate postoperative plain radiographs and computed tomography (CT) scans were compared with the most recent plain and dynamic radiographs to assess changes in spinal growth and alignment. Seventeen children met entry criteria for the study. All patients had fusion documented on follow-up radiography or CT scans. At a mean follow up of 28 months, there were no cases of sagittal malalignment (kyphotic or swan-neck deformity), subaxial instability (osteophyte formation or subluxation), or unintended fusion of adjacent levels. The lordotic curvature of the cervical spine increased from a mean of 15 degrees postoperatively to 27 degrees at follow up (p = 0.06). A mean of 34% of the vertical growth of the cervical spine occurred within the fusion segment. When data were analyzed pertaining to a subgroup of five patients who underwent follow-up periods for longer than 48 months (mean 50.2 months, range 48-54 months), similar results were seen. CONCLUSIONS: Preliminary follow-up results indicate that, compared with older children, children 6 years of age or younger undergoing OC or C1-2 fusion are not at an increased risk of spinal deformity or subaxial instability. Longer follow-up periods, during which measurements of the spinal canal are taken, will be necessary to determine precisely how children's spines grow and remodel after an upper cervical spine fusion.

Age Factors↗
PubMed2005

Harvey Cushing and Oskar Hirsch: early forefathers of modern transsphenoidal surgery.

The transnasal transsphenoidal approach is the preferred route for removal of most lesions of the sella turcica. The concept of transnasal surgery traversing the sphenoid sinus to reach the sella has existed for nearly a century. A comprehensive historical overview of the evolution of transsphenoidal surgery has been reported previously. In the present vignette, the authors focus on transsphenoidal surgery in the early 1900s, particularly on the methods advocated by Harvey Cushing and Oskar Hirsch, two prominent pituitary surgeons who pioneered the transsphenoidal technique. Cushing championed the sublabial approach, whereas Hirsch was the master of the endonasal route. Coincidentally, both surgeons independently performed the submucous septal resection for the first time on June 4, 1910. Although Cushing's and Hirsch's approaches were predicated on the work of their predecessors, their transsphenoidal procedures became the two most popular techniques and, for future generations of pituitary surgeons, laid the foundation for modem transsphenoidal surgery. In this comparative analysis, the authors compare the operative nuances of the approaches of Cushing and Hirsch and describe the contributions of these pioneers to modern transsphenoidal surgery.

Austria↗
PubMed2004

Oligodendroglioma and juvenile pilocytic astrocytoma presenting as synchronous primary brain tumors. Case report with histological and molecular differentiation of the tumors and review of the literature.

Multiple metastatic brain tumors and multifocal primary brain tumors of a single histological type are well described in the literature. The concurrent presence of multiple primary brain tumors with different histological characteristics, however, is very rare. The authors describe the first known case in which an oligodendroglioma and a juvenile pilocytic astrocytoma (JPA) presented as synchronous primary brain tumors in the same patient. This 43-year-old man presented with a 2-month history of progressive headaches, nausea, and vomiting. Magnetic resonance imaging demonstrated an enhancing heterogeneous right medial cerebellar lesion and a larger calcified, nonenhancing, heterogeneous right frontal lesion with surrounding edema and a mass effect. The results of a metastatic workup were unremarkable. The patient underwent an initial right frontotemporal craniotomy and a subsequent suboccipital craniectomy 2 years later for resection of the posterior fossa lesion. Histological examination revealed the frontal and cerebellar lesions to be an oligodendroglioma and JPA, respectively. A molecular analysis detected a deletion of chromosome 1p36 in the oligodendroglioma, but not in the JPA. After the initial operation, the patient received follow-up care for his oligodendroglioma, but eventually required temozolomide for tumor progression. His condition remains stable both neurologically and according to imaging studies. The authors describe the first known case in which a low-grade oligodendroglioma and a JPA presented as synchronous primary brain tumors. They review the literature on multiple primary brain tumors with different histological characteristics and discuss potential mechanisms for the development of these lesions.

Adult↗
PubMed2004

Complications of intracranial pressure monitoring in children with head trauma.

OBJECT: Intracranial pressure (ICP) monitoring has become routine in the management of patients with traumatic brain injury (TBI). Many surgeons prefer to use external ventricular drains (EVDs) over fiberoptic monitors to measure ICP because of the added benefit of cerebrospinal fluid drainage. The purpose of this study was to examine a consecutive series of children with TBI and compare the incidence of complications after placement of an EVD, a fiberoptic intraparencyhmal monitor, or both. METHODS: A retrospective chart review was conducted to identify children with TBI who met the criteria for insertion of an ICP monitor. All patients underwent head CT scanning on admission and after placement of an ICP monitor. During a 5-year period 80 children met the criteria for inclusion in the study. Eighteen children (22.5%) underwent EVD placement only, 18 (22.5%) underwent placement of a fiberoptic device only, and 44 (55%) received both. A total of 62 fiberoptic devices (48%) were inserted, and 68 EVDs (52%) were placed. Overall, there was a fourfold increased risk of complications in children who received an EVD compared with those in whom a fiberoptic monitor was placed (p = 0.004). Hemorrhagic complications were detected in 12 (17.6%) of 62 patients who received an EVD compared with four (6.5%) of 62 patients who received a fiberoptic monitor (p = 0.025). Six (8.8%) of 68 EVDs were malpositioned and required replacement; in three (50%) of these cases a hemorrhagic complication occurred. Only one infection was noted in a patient with an EVD (1.5%). CONCLUSIONS: In this retrospective cohort of pediatric patients with TBI, complication rates were significantly higher in those receiving EVDs than in those in whom fiberoptic monitors were placed. Although the majority of these complications did not entail clinical sequelae, surgeons should be aware of the different complication rates when choosing the most appropriate device for each patient.

Adolescent↗
PubMed2003

Diffuse large B-cell lymphoma presenting as a sacral tumor. Report of two cases.

Primary lymphomas of the sacrum are rare tumors, reported only in a few cases in the literature. The authors describe two patients with diffuse large B-cell lymphomas presenting as a sacral tumor. In the first case a 52-year-old man presented with progressive back pain, bilateral radicular pain, and saddle block anesthesia secondary to a lytic, expansile soft-tissue mass. The mass arose from the sacrum and eroded through the right S-1 to S-4 foramina and extended into the epidural space of the spinal canal. On magnetic resonance imaging, the sacral mass enhanced homogeneously with Gd. In the second case a 64-year-old man presented with left-sided radicular pain, paresthesias, and progressive weakness due to a lytic soft-tissue mass in the left sacral ala extending into the left L-5 and S-1 foramina. Metastatic workup in each patient demonstrated unremarkable findings. In both cases, an open biopsy procedure was performed after nondiagnostic examination of needle biopsy samples. Histopathological examination showed evidence consistent with diffuse large B-cell lymphoma in both patients. In the first case the disease was classified as Stage IAE, and the patient subsequently underwent four cycles of cyclophosphamide/doxorubicin/vincristine/prednisone (CHOP)- and rituximab-based chemotherapy followed by consolidation radiotherapy. In the second case the disease was also classified as Stage IAE, and the patient underwent CHOP-based chemotherapy and consolidation radiotherapy. In both cases radiography demonstrated a decrease in size of the sacral lymphomas. The authors review the clinical, radiological, and histological features of sacral lymphomas. Lymphoma should be considered in the differential diagnosis of sacral tumors.

Antibodies, Monoclonal↗
PubMed2003

Spinal meningiomas: surgical management and outcome.

Advances in imaging and surgical technique have improved the treatment of spinal meningiomas; these include magnetic resonance imaging, intraoperative ultrasonography, neuromonitoring, the operative microscope, and ultrasonic cavitation aspirators. This study is a retrospective review of all patients treated at a single institution and with a pathologically confirmed diagnosis of spinal meningioma. Additionally the authors analyze data obtained in 556 patients reported in six large series in the literature, evaluating surgical techniques, results, and functional outcomes. Overall, surgical treatment of spinal meningiomas is associated with favorable outcomes. Spinal meningiomas can be completely resected, are associated with postoperative functional improvement, and the rate of recurrence is low.

Aged↗