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René O. Mirimanoff, Daniel E. Dosoretz, Rita M. Linggood, Robert G. Ojemann and Robert L. Martuza

✓ The rates of survival, tumor recurrence, and tumor progression were analyzed in 225 patients with meningioma who underwent surgery as the only treatment modality between 1962 and 1980. Patients were considered to have a recurrence if their studies verified a mass effect in spite of a complete surgical removal, whereas they were defined as having progression if, after a subtotal excision, there was clear radiological documentation of an increase in the size of their tumor. There were 168 females and 57 males (a ratio of 2.9:1), with a peak incidence of tumor occurrence in the fifth (23%), sixth (29%), and seventh (23%) decades of life. Anatomical locations were the convexity (21%), parasagittal area (17%), sphenoid ridge (16%), posterior fossa (14%), parasellar region (12%), olfactory groove (10%), spine (8%), and orbit (2%). The absolute 5-, 10-, and 15-year survival rates were 83%, 77%, and 69%, respectively.

Following a total resection, the recurrence-free rate at 5, 10, and 15 years was 93%, 80%, and 68%, respectively, at all sites. In contrast, after a subtotal resection, the progression-free rate was only 63%, 45%, and 9% during the same period (p < 0.0001). The probability of having a second operation following a total excision after 5, 10, and 15 years was 6%, 15%, and 20%, whereas after a subtotal excision the probability was 25%, 44%, and 84%, respectively (p < 0.0001). Tumor sites associated with a high percentage of total excisions had a low recurrence/progression rate. For example, 96% of convexity meningiomas were removed in toto, and the recurrence/progression rate at 5 years was only 3%. Parasellar meningiomas, with a 57% total excision rate, had a 5-year probability of recurrence/progression of 19%. Only 28% of sphenoid ridge meningiomas were totally resected, and at 5 years the probability of recurrence/progression was 34%. In patients undergoing a second resection, the probability of a third operation at 5 and 10 years was 42% and 56%, respectively. There was no difference in the recurrence/progression rates according to the patients' age or sex, or the duration of symptoms. Implications for the potential role of adjunctive medical therapy or radiation therapy for meningiomas are discussed.

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Robert G. Ojemann, Robert A. Levine, William M. Montgomery and Patricia McGaffigan

✓ Twenty-two patients with unilateral acoustic neuromas and preoperative speech discrimination scores of 35% or more had intraoperative monitoring of the electrocochleogram (ECoG) using a transtympanic electrode, and of the brain-stem auditory evoked potentials (BAEP's) using scalp electrodes. Rapid feedback was provided about the status of the cochlear microphonics from the hair cells of the inner ear (CM of the ECoG), the compound action potential of the auditory nerve (N-1 of the ECoG or Wave I of the BAEP's) and the potentials from the lower brain stem (Wave V of the BAEP's). All patients had total removal of the tumor. In 21, the cochlear nerve was anatomically preserved, and 20 had good postoperative facial nerve function. Correlation of tumor size with postoperative hearing was as follows: discrimination scores of more than 35% in three of four patients with 1-cm tumors, two of eight with 1.5-cm tumors, two of six with 2- to 2.5-cm tumors, and one of four with tumors of 3 cm or more. Two other patients with 1.5-cm tumors had discrimination scores of less than 35%, and one patient with a 2-cm tumor had only sound perception. In two patients, the discrimination scores improved. At the end of the operation, all patients with hearing had a detectable N-1, and, when recorded, CM. All but one patient with no hearing had lost N-1, and CM was absent or reduced. Unless Wave V was unchanged, it was a poor predictor of postoperative hearing, and its absence did not preclude preservation of good hearing.

The electrophysiological changes during each stage of the operation were analyzed and correlated with events during surgery. Areas in which there was an increased risk of loss of the potentials were determined. In some patients monitoring was unnecessary, because either there were no significant changes or the changes were abrupt and no recovery occurred. However, in other patients, monitoring alerted the surgeon to a possible problem and the method of dissection was altered. Possible mechanisms of hearing loss were suggested from the changes in the recordings.

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G. Andrew James, Shanti Prakash Tripathi, Jeffrey G. Ojemann, Robert E. Gross and Daniel L. Drane

Object

Functional neuroimaging has shown that the brain organizes into several independent networks of spontaneously coactivated regions during wakeful rest (resting state). Previous research has suggested that 1 such network, the default mode network (DMN), shows diminished recruitment of the hippocampus with temporal lobe epilepsy (TLE). This work seeks to elucidate how hippocampal recruitment into the DMN varies by hemisphere of epileptogenic focus.

Methods

The authors addressed this issue using functional MRI to assess resting-state DMN connectivity in 38 participants (23 control participants, 7 patients with TLE and left-sided epileptogenic foci, and 8 patients with TLE and right-sided foci). Independent component analysis was conducted to identify resting-state brain networks from control participants' data. The DMN was identified and deconstructed into its individual regions of interest (ROIs). The functional connectivity of these ROIs was analyzed both by hemisphere (left vs right) and by laterality to the epileptogenic focus (ipsilateral vs contralateral).

Results

This attempt to replicate previously published methods with this data set showed that patients with left-sided TLE had reduced connectivity between the posterior cingulate (PCC) and both the left (p = 0.012) and right (p < 0.002) hippocampus, while patients with right-sided TLE showed reduced connectivity between the PCC and right hippocampus (p < 0.004). After recoding ROIs by laterality, significantly diminished functional connectivity was observed between the PCC and hippocampus of both hemispheres (ipsilateral hippocampus, p < 0.001; contralateral hippocampus, p = 0.017) in patients with TLE compared with control participants. Regression analyses showed the reduced DMN recruitment of the ipsilateral hippocampus and parahippocampal gyrus (PHG) to be independent of clinical variables including hippocampal sclerosis, seizure frequency, and duration of illness. The graph theory metric of strength (or mean absolute correlation) showed significantly reduced connectivity of the ipsilateral hippocampus and ipsilateral PHG in patients with TLE compared with controls (hippocampus: p = 0.028; PHG: p = 0.021, after correction for false discovery rate). Finally, these hemispheric asymmetries in strength were observed in patients with TLE that corresponded to hemisphere of epileptogenic focus; 87% of patients with TLE had weaker ipsilateral hippocampus strength (compared with the contralateral hippocampus), and 80% of patients had weaker ipsilateral PHG strength.

Conclusions

This study demonstrated that recoding brain regions by the laterality to their epileptogenic focus increases the power of statistical approaches for finding interhemispheric differences in brain function. Using this approach, the authors showed TLE to selectively diminish connectivity of the hippocampus and parahippocampus in the hemisphere of the epileptogenic focus. This approach may prove to be a useful method for determining the seizure onset zone with TLE, and could be broadly applied to other neurological disorders with a lateralized onset.

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Robert T. Buckley, Tiffany Morgan, Russell P. Saneto, Jason Barber, Richard G. Ellenbogen and Jeffrey G. Ojemann

Object

Functional hemispherectomy is a well-recognized surgical option for the treatment of unihemispheric medically intractable epilepsy. While the resultant motor deficits are a well-known and expected consequence of the procedure, the impact on other cortical functions has been less well defined. As the cortical control of swallowing would appear to be threatened after hemispherectomy, the authors retrospectively studied a pediatric population that underwent functional hemispherectomy for medically intractable epilepsy to characterize the incidence and severity of dysphagia after surgery.

Methods

A retrospective cohort (n = 39) of pediatric patients who underwent hemispherectomy at a single institution was identified, and available clinical records were reviewed. Additionally, the authors examined available MR images for integrity of the thalamus and basal ganglia before and after hemispherectomy. Clinical and video fluoroscopic assessments of speech pathology were reviewed, and the presence, type, and duration of pre- and postoperative dysphagia were recorded.

Results

New-onset, transient dysphagia occurred in 26% of patients after hemispherectomy along with worsening of preexisting dysphagia noted in an additional 15%. Clinical symptoms lasted a median of 19 days. Increased duration of symptoms was seen with late (> 14 days postoperative) pharyngeal swallow dysfunction when compared with oral dysphagia alone. Neonatal stroke as a cause for seizures decreased the likelihood of postoperative dysphagia. There was no association with seizure freedom or postoperative hydrocephalus.

Conclusions

New-onset dysphagia is a frequent and clinically significant consequence of hemispherectomy for intractable epilepsy in pediatric patients. This dysphagia was always self-limited except in those patients in whom preexisting dysphagia was noted.

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William T. Curry Jr., G. Rees Cosgrove, Bradley R. Buchbinder and Robert G. Ojemann

Intraventricular meningiomas of the lateral ventricle occur relatively rarely, but they are often large at the time of detection and present more commonly on the left side. Although the ability to resect these tumors safely has greatly improved over time, standard surgical approaches often traverse cortex close to areas of specific cortical function. Precise cortical mapping of language and sensorimotor cortices can be accomplished noninvasively by using functional magnetic resonance (fMR) imaging. The authors used fMR imaging in planning the cortical incision for resection of a large intraventricular trigone meningioma in the dominant hemisphere of a patient who, postoperatively, suffered no aphasia or hemiparesis. The authors discuss the advantages of mapping cortical function preoperatively with fMR imaging when approaching intraventricular lesions.

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Edward Tarlov, Henry Schmidek, R. Michael Scott, James G. Wepsic and Robert G. Ojemann

✓ Postoperative changes in blood pressure regulation were studied retrospectively in 56 patients and prospectively in 46 patients after carotid endarterectomy. Hypotension, of a degree sufficient to require pressors and/or volume-expanding agents to maintain systolic blood pressure above 100 mm Hg, associated with bradycardia and low central venous pressure occurred in 41% of the retrospectively studied group. In the prospectively studied group, controllable variables were excluded by standardizing fluid management and anesthetic technique. It was found that infusion of colloid preoperatively, intraoperatively, and postoperatively to maintain central venous pressure above zero markedly reduced the incidence of postoperative hypotension. Denervation of the carotid sinus prevented postoperative hypotension. We hypothesize that the atheromatous plaque damps the pressure wave reaching the carotid sinus baroreceptors. Removal of the plaque results in increased stimulation of these baroreceptors, with a resulting bradycardia and hypotension of neurogenic origin. The data indicate that blood pressure usually returns to its previous level within a few hours. Closely monitored infusion of colloid before, during, and after operation is the recommended form of management.

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Robert T. Buckley, Anthony C. Wang, John W. Miller, Edward J. Novotny and Jeffrey G. Ojemann

OBJECTIVE

Laser ablation is a novel, minimally invasive procedure that utilizes MRI-guided thermal energy to treat epileptogenic and other brain lesions. In addition to treatment of mesial temporal lobe epilepsy, laser ablation is increasingly being used to target deep or inoperable lesions, including hypothalamic hamartoma (HH), subependymal giant cell astrocytoma (SEGA), and exophytic intrinsic hypothalamic/third ventricular tumors. The authors reviewed their early institutional experience with these patients to characterize clinical outcomes in patients undergoing this procedure.

METHODS

A retrospective cohort (n = 12) of patients undergoing laser ablation at a single institution was identified, and clinical and radiographic records were reviewed.

RESULTS

Laser ablation was successfully performed in all patients. No permanent neurological or endocrine complications occurred; 2 (17%) patients developed acute obstructive hydrocephalus or shunt malfunction following treatment. Laser ablation of HH resulted in seizure freedom (Engel Class I) in 67%, with the remaining patients having a clinically significant reduction in seizure frequency of greater than 90% compared with preoperative baseline (Engel Class IIB). Treatment of SEGAs resulted in durable clinical and radiographic tumor control in 2 of 3 cases, with one patient receiving adjuvant everolimus and the other receiving no additional therapy. Palliative ablation of hypothalamic/third ventricular tumors resulted in partial tumor control in 1 of 3 patients.

CONCLUSIONS

Early experience suggests that laser ablation is a generally safe, durable, and effective treatment for patients harboring HHs. It also appears effective for local control of SEGAs, especially in combination therapy with everolimus. Its use as a palliative treatment for intrinsic hypothalamic/deep intraventricular tumors was less successful and associated with a higher risk of serious complications. Additional experience and long-term follow-up will be beneficial in further characterizing the effectiveness and risk profile of laser ablation in treating these lesions in comparison with conventional resective surgery or stereotactic radiosurgery.

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Stephen B. Tatter, Christopher S. Ogilvy, Jeffrey A. Golden, Robert G. Ojemann and David N. Louis

✓ Two cases are reported of third ventricle masses that were clinically and radiographically indistinguishable from pure colloid cysts. A 21- and a 36-year-old man presented with 5-year and 10-day histories of headache, respectively. Magnetic resonance (MR) imaging revealed smooth, homogeneous masses in the anterior third ventricle that were iso- to hyperintense on T1-weighted MR images and hyperintense on T2-weighted images. There was little enhancement with intravenous contrast material. In both patients, craniotomies were performed and histopathological examination revealed xanthogranulomas of the choroid plexus with only microscopic foci of colloid cyst-like structures. These cases illustrate that xanthogranulomas of the third ventricle may clinically and radiologically mimic pure colloid cysts, that a range of MR imaging signals can be seen, and that craniotomy rather than stereotactic aspiration is the indicated treatment.