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Biomedical subjects

L Sekhar

Publications and source records attributed to L Sekhar.

17 recordsLinked to original sources
PubMed1997

Multiple neoplasms following craniospinal irradiation for medulloblastoma in a patient with nevoid basal cell carcinoma syndrome. Case report.

A 28-year-old man presented to the authors' hospital with multiple intracranial tumors. At 2 years of age, he had undergone resection of a medulloblastoma and received adjunctive craniospinal irradiation. Subsequently, he was diagnosed with nevoid basal cell carcinoma syndrome, Gorlin's syndrome. Since his first presentation, he has required surgery for multiple basal cell carcinomas, an osteochondroma of the rib, two meningiomas, a trigeminal schwannoma, and a pleomorphic liposarcoma, all of which arose within the radiation field. Despite this impressive list of benign and malignant neoplasms, the patient is relatively well and leads a normal life. The authors examine the relationships between Gorlin's syndrome and radiation therapy and the subsequent development of tumors.

Adult↗
PubMed1995

Outcomes analysis in cranial base surgery - preliminary results.

A system of analysis addressing predictors of management outcomes in Cranial Base Surgery has yet to be published. We therefore report data on seventy-nine consecutive patients undergoing surgery for tumors involving the cranial base, excluding patients with the diagnosis of pituitary microadenoma. Outcomes were defined prospectively in terms of completeness of tumor resection, complications of treatment with emphasis on neurological morbidity, and return to work or independent living. Also, preoperative features are analyzed as influencing cost of treatment, estimated in terms of the number of surgical procedures required, duration of hospital and Intensive Care Unit stay, and time taken to return to work. Preliminary analysis of data reveals that severe brainstem compression, large tumor size (average diameter > 3 cm), high cavernous sinus grade, and tumor encasement of major cerebral arteries are associated with incomplete tumor resection (p < 0.05). Patient age greater than 65, preoperative Karnofsky Performance Score (KPS) less than 80, and severe brainstem compression are associated with increased risk of stroke (p < 0.05). Age greater than 65 and preoperative KPS less than 80 are associated with an increased length of stay (p < 0.05). Other untoward events did not occur with sufficient frequency to reach statistical significance. A model of outcomes analysis in Cranial Base Surgery is proposed utilizing a database to incorporate a group of non-operated patients and include quality of life measurements in long-term patient follow-up.

Brain Neoplasms↗
PubMed1994

Treatment of paranasal sinus cancer with cranial base surgery: results.

Paranasal sinus cancer has been difficult to treat with surgery. A significant negative factor has been the high frequency of tumor-positive surgical margins. The goal of this study was to evaluate the effectiveness of cranial base surgery in achieving higher tumor-free resective margins and its impact on the disease control. Fifty patients with paranasal sinus cancer were treated with cranial base surgery and retrospectively evaluated. Surgery was performed for both primary and recurrent disease ("salvage"), with more than half of the surgeries being salvage procedures. The survival at 40 months of mean follow-up is 74%, and 64% of the patients either have no evidence of disease (NED) or have died of other causes (DOC). Cranial base surgery is an effective treatment of paranasal sinus cancer. The ability to achieve tumor-free surgical margins (77% in squamous cell carcinoma [SCC]) is directly related to NED status (75% of NED patients had free margins).

Adenocarcinoma↗
PubMed1994

Transcranial Doppler ultrasonography with induction of anesthesia for neurosurgery.

Intracranial hypertension can occur with induction of anesthesia; however, the clinical significance of this is unclear. We used transcranial Doppler (TCD) ultrasonography in neurosurgical patients during induction of anesthesia and endotracheal intubation to assess the incidence of high intracranial pressure (ICP) waveforms and to correlate TCD observations with specific anesthetics and anesthetic regimens. The middle cerebral artery was monitored by TCD during induction of anesthesia and endotracheal intubation in 196 patients undergoing elective neurosurgery. Middle cerebral artery blood flow velocity (MCABFV) and physiologic data were observed continuously and recorded at the following times: preinduction, induction, intubation, and postintubation. Induction with thiopental or etomidate decreased MCABFV, intubation increased MCABFV, and postintubation ventilation decreased MCABFV. MCABFV was higher throughout the induction sequence in the 92 patients with tumors. Although there were numerous individual exceptions, changes in mean arterial pressure correlated statistically with changes in MCABFV. No patient had an end-diastolic flow velocity of 0. We reached the following conclusions: (a) TCD is a straightforward modality that can be used to monitor dynamic cerebrovascular events during induction of anesthesia; (b) MCABFV is increased with brain tumors; (c) thiopental and etomidate rapidly decrease and intubation rapidly increases MCABFV; and (d) routine TCD monitoring for high ICP waveforms during anesthetic induction for routine elective neurosurgery appears to be unwarranted.

Adult↗
PubMed1994

Partial hypoglossal to facial nerve anastomosis for reinnervation of the paralyzed face in patients with lower cranial nerve palsies: technical note.

Reanimation of the paralyzed face in patients who have coexisting lower cranial nerve palsies is a difficult management problem. Classic hypoglossal to facial nerve anastomosis may be devastating in these already compromised patients. We describe a technique of partial hypoglossal to facial anastomosis that can preserve hypoglossal nerve function and provide adequate facial reanimation.

Adult↗
PubMed1993

Assessing brain stem function.

Intraoperative neurophysiologic monitoring provides objective measures of nervous system function that are of value when operating in proximity to the brain stem. Real-time measurements of function can be correlated to operative manipulations in order to reduce the risk of damage in critically important regions. Techniques for evaluating brain stem function clinically and electrophysiologically are presented along with their applications during surgery of the brain stem.

Brain Diseases↗
PubMed1991

Computerized tomography and magnetic resonance imaging following cranial base surgery.

The computed tomography scans and magnetic resonance imaging films of 57 patients who underwent anterior or anterolateral cranial base surgery from January 1987 to August 1989 were retrospectively reviewed to ascertain the significance of early and late postoperative intracranial imaging changes. Extra-axial changes (air, blood, cerebrospinal fluid collection) were found in 96% of patients; axial changes (brain edema, contusion) were seen in 30% of patients in the first postoperative period (72 hours). Subsequently, extra-axial changes began to resolve but axial changes became more prevalent. After 6 months, only axial changes persisted (encephalomalacia). It was encouraging to find a low correlation of imaging abnormalities with clinically significant findings.

Encephalomalacia↗
PubMed1989

Determination of irreversible ischemia by xenon-enhanced computed tomographic monitoring of cerebral blood flow in patients with symptomatic vasospasm.

In patients with subarachnoid hemorrhage, delayed neurological deficits, often followed by infarction, are believed to result from ischemia caused by vasospasm. Cerebral blood flow (CBF) data have been useful in predicting the risk of vasospasm in these patients and in distinguishing those deficits caused by vasospasm. Although CBF thresholds for infarction have been established in animals, few clinical studies have correlated CBF values with neurological symptoms and infarction. To assess the sensitivity to ischemia provided by xenon-enhanced computed tomography (Xe/CT) of CBF and to define the clinical significance of specific values that it measures, we compared the clinical, CT, and Xe/CT findings on CBF in 51 patients with subarachnoid hemorrhage caused by ruptured aneurysms. Each patient had 1 to 6 Xe/CT studies. Fourteen patients had symptomatic vasospasm. In all 14, the first post deficit Xe/CT study found abruptly reduced CBF, either regionally or globally. In 9 of these 14 patients, flow values fell below 15 ml/100 g/min in 2 or more adjacent 2-cm cortical regions of interest, and in all 9, concurrent follow-up CT scans showed infarction in these regions. Eight of the 9 had paralysis and a severe sensory deficit. No patient whose CBF remained above 18 ml/100 g/min developed infarction. The blood flow studies caused neither significant complications nor neurological deterioration. The Xe/CT CBF method appears very sensitive to the early detection of symptomatic vasospasm. In most patients with subarachnoid hemorrhage, this noninvasive technique can replace angiography to delineate the location and severity of vasospasm, and may be useful in predicting the development of infarction.

Blood Flow Velocity↗
PubMed1987

An acoustic aneurysm-detector.

Intracranial aneurysms have a high prevalence in the adult population; and if they rupture, significant morbidity almost always ensues. However, pulsatile blood flow through aneurysms produces vibrational sound patterns that may be detected extracranially. Thus, an acoustic aneurysm-detector has been developed to detect the sounds produced by intracranial aneurysms prior to rupture. The design is based on the utilization of a hydrophone for signal detection and computational signal processing for signal extraction. Data are examined in the time domain, the frequency domain, and the time-frequency plane. Examples are presented from an animal model and from a patient with a known aneurysm.

Adult↗
PubMed1986

Diagnosis and surgical treatment of disabling positional vertigo.

This report reviews the characteristic symptoms of disabling positional vertigo (DPV), and the tests used to reach a differential diagnosis of this disorder. Twenty-one patients were operated on consecutively for management of DPV between March, 1983, and September, 1984. In all patients one or more arteries or veins was found to be compressing the eighth cranial nerve when the nerve was exposed for microvascular decompression to relieve the symptoms of DPV. After the operation, 16 of the 21 patients were free of symptoms, or symptoms were so much improved that the patients returned to normal work or social life. Two patients had no improvement and three had limited relief of symptoms postoperatively. None of the patients experienced hearing loss as a result of the operation to relieve DPV, but one patient suffered a cerebellar contusion during the operation.

Adolescent↗
PubMedDate not supplied

Antibiotic prophylaxis in cranial base surgery.

The role of perioperative antibiotic prophylaxis was investigated in 95 patients undergoing 100 clean-contaminated cranial base surgeries. A variety of antibiotic regimens were employed. Potential risk factors for local infection were analyzed. Seven patients (7%) developed infections at the surgical site (meningitis, intracranial abscess, cellulitis/abscess, and osteomyelitis). Antibiotic prophylaxis for 24 hours or less was associated with a significantly increased risk of infection (p less than 0.04). Prolonged antibiotic prophylaxis (greater than 48 hours) was not more efficacious than prophylaxis for 48 hours. The surgical approach, type of reconstruction, duration of surgery, and use of drains were not significantly correlated with wound infection. The risk of intracranial infection following cranial base surgery is low despite the presence of bacterial contamination intraoperatively. Broad-spectrum coverage of gram-positive and gram-negative organisms for at least 48 hours is recommended. Attention to surgical technique is important in preventing infectious complications.

Adolescent↗
PubMedDate not supplied

Xe/CT cerebral blood flow evaluation of delayed symptomatic cerebral ischemia after subarachnoid hemorrhage.

PURPOSE: We examined the xenon/CT method of measuring cerebral blood flow in assessing the location, pattern of onset, and severity of delayed cerebral ischemia. PATIENTS AND METHODS: Fourteen patients with delayed neurologic deficits due to ischemia were selected from a group of 66 patients with subarachnoid hemorrhage. All blood flow studies were performed within 12 hours of deterioration and at regular intervals during medical management. RESULTS: In 10 of the 14 patients, noncontrast CT did not identify a cause for deterioration, whereas the blood flow study revealed diminished flow values. Location of blood flow reduction was variable. In five of the 14 patients, blood flow reduction was closely related anatomically to the vessel of aneurysm origin. In another three, blood flow reduction was anatomically remote to the vessel of origin. The remaining six experienced local and remote cerebral blood flow reduction. Six of 14 patients suffered sudden, devastating deterioration, refractory to therapy and associated with blood flow of 15 cc/100 g.min or less, resulting in local or widespread infarction. The remaining eight had less severe blood flow reduction and did not infarct those territories. CONCLUSIONS: Vasospasm can affect remote vessels as severely as local vessels and can affect remote vessels alone. Diminished cerebral blood flow correlated closely with clinical vasospasm in this group of patients. Xenon/CT cerebral blood flow studies can identify tissue at risk of infarction when CT is normal.

Adult↗
PubMedDate not supplied

Sinus pericranii: CT and MR findings.

A case of sinus pericranii communicating with the right transverse sinus is reported. The radiographic findings on CT, angiography, and magnetic resonance imaging are presented.

Adult↗
PubMedDate not supplied

Balloon test occlusion of the internal carotid artery with stable xenon/CT cerebral blood flow imaging.

We describe a technique to predict preoperatively the safety of permanently occluding an internal carotid artery. The method was performed by imaging stable xenon cerebral blood flow (CBF) with the internal carotid artery both open and temporarily occluded with a nondetachable balloon on a double lumen Swan-Ganz catheter. Patients were those in whom we planned to sacrifice the internal carotid artery (those with giant or inaccessible aneurysms) or those in whom such a sacrifice was at least likely (those with skull base tumors). Patients were divided into three groups on the basis of a comparison of occluded and nonoccluded CBF values. Group-I patients had no significant change in CBF with internal carotid artery occlusion; group-II patients showed a symmetric decrease in CBF; and group-III patients had an asymmetric decrease in CBF, always greater on the occluded side. A fourth group clinically failed to tolerate even brief carotid occlusion. The internal carotid artery in one patients from group III was sacrificed at surgery: the size and shape of his postoperative infarct corresponded almost exactly to the area of asymmetrically decreased CBF on his occluded study. The data suggest that if surgery is likely to result in permanent occlusion of the internal carotid artery, then patients who are at risk for delayed neurologic injury due to a compromised cerebral blood flow should have arterial bypass grafts before such surgery is performed.

Brain Ischemia↗