Biomedical subjects

T H Schwartz

Publications and source records attributed to T H Schwartz.

At least 19 recordsLinked to original sources

PubMed2001

Extended frontal approach with bilateral orbitofrontoethmoidal osteotomies for removal of a giant extracranial schwannoma in the nasopharynx, sphenoid sinus, and parapharyngeal space.

BACKGROUND: Although parapharyngeal schwannomas are not uncommon, schwannomas of the nasopharynx and paranasal sinuses are rare lesions. In the absence of intracranial extension, they are usually removed with transantral, lateral rhinotomy or more complex transfacial approaches. CASE DESCRIPTION: We report a 24-year-old patient with a giant benign schwannoma involving the superior parapharyngeal space, pterygopalatine fossa, nasopharynx, and sphenoid sinus with erosion into the clivus that was removed with an extended frontal approach including bilateral orbitofrontoethmoidal osteotomies. CONCLUSION: The advantages of the extended subfrontal over more standard transfacial approaches for lesions in this location include the early dissection of critical neural structures, preserving cosmetics and facilitating management of an inadvertent cerebrospinal fluid leak.

Adult↗

PubMed2001

In vivo optical mapping of epileptic foci and surround inhibition in ferret cerebral cortex.

The population of neurons participating in an epileptiform event varies from moment to moment. Most techniques currently used to localize epileptiform events in vivo have spatial and/or temporal sampling limitations. Here we show in an animal model that optical imaging based on intrinsic signals is an excellent method for in vivo mapping of clinically relevant epileptiform events, such as interictal spikes, ictal onsets, ictal spread and secondary homotopic foci. In addition, a decrease in the optical signal correlates spatially with a decrease in neuronal activity recorded from cortex surrounding an epileptic focus. Optical mapping of epilepsy might be a useful adjunct in the surgical treatment of neocortical epilepsy, which critically depends on the precise localization of intrinsically epileptogenic neurons.

Animals↗

PubMed2001

Strategies for reoperation after comprehensive epilepsy surgery.

OBJECT: Prior reports of seizure control following reoperation for failed epilepsy surgery have shown good results. These studies included patients who presented during the era preceding magnetic resonance (MR) imaging, and the patients were often not monitored intracranially or underwent subtotal hippocampal resections. In this study, the authors hypothesized that reoperation for recurrent seizures following a more comprehensive initial workup and surgery would not yield such good results. METHODS: The authors examined a consecutive series of patients who underwent two operations at Yale-New Haven Hospital for medically intractable epilepsy and in whom there was a minimum of 1-year follow up after the second surgery. All patients were evaluated and treated according to a standard protocol, including preoperative MR imaging, a low threshold for invasive monitoring, and a radical amygdalohippocampectomy when indicated. Twenty-seven patients were identified (five with mesial temporal sclerosis, 20 with neocortical disease, and two with multifocal sites of seizure onset) of whom six (22%) underwent intentionally palliative second surgery (corpus callostomy or placement of a vagus nerve stimulator [VNS]). Of the remaining 21 patients, only four (19%) became seizure free after a second resective operation. The most common causes of treatment failure were dual pathology, recurrent tumor, limited resection to preserve function, widespread developmental abnormalities, and electrographic sampling error. Successful outcomes resulted from removal of recurrent tumors, completion of a functional hemispherectomy, or repeated invasive monitoring to correct a sampling error. Five (83%) of the six intentionally palliative second operations resulted in more than a 50% decrease in seizure frequency. CONCLUSIONS: If an aggressive preoperative evaluation and surgical resection are performed, reoperation for recurrent seizures has a much lower likelihood of cure than previously reported. Intentionally palliative surgery such as placement of a VNS unit may be considered for patients in whom the initial operation fails to decrease seizure frequency.

Adolescent↗

PubMed2000

Intramedullary ependymomas: clinical presentation, surgical treatment strategies and prognosis.

Intramedullary ependymomas are rare tumors but comprise the majority of intramedullary glial neoplasms in the adult. These tumors are benign, slow-growing lesions which are optimally treated with gross-total surgical resection without adjuvant therapy. This objective can be attained safely in a majority, of patients. Post-operative functional outcome is related to pre-operative functional status. Hence, early diagnosis, prior to symptomatic progression, is critical to the successful treatment of these tumors. Adjuvant therapy is indicated for the rare malignant or disseminated tumor or following sub-total resection.

Adult↗

PubMed2000

Non-neoplastic intramedullary pathology. Diagnostic dilemma: to Bx or not to Bx.

There are several non-neoplastic lesions which may mimic intramedullary spinal cord neoplasm in their radiographic and clinical presentation. These can be classified as either infectious (TB, fungal, bacterial, parasitic, syphilis, CMV, HSV) and non-infectious (sarcoid, MS, myelitis, ADEM, SLE) inflammatory lesions, idiopathic necrotizing myelopathy, unusual vascular lesions (amyloid, infarct, isolated intramedullary vascular lesions) and radiation myelopathy. Although biopsy may be indicated in many cases, the mistaken diagnosis of intramedullary neoplasm can often be eliminated pre-operatively.

Amyloidosis↗

PubMed2000

Quadrigeminal variant of perimesencephalic nonaneurysmal subarachnoid hemorrhage.

OBJECTIVE: Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSH) is a benign entity with a low risk of rebleeding. The most widely accepted definition emphasizes the presence of blood ventral to the midbrain or pons on early computed tomography. We sought to determine the frequency of PNSH with blood centered in the quadrigeminal cistern. METHODS: We reviewed a prospectively collected database of all patients admitted to our institution over a 2.5-year period with subarachnoid hemorrhage (SAH) and identified PNSH patients from early computed tomographic scans and negative four-vessel angiograms. RESULTS: Of 220 SAH patients, we identified 9 with PNSH. Two (22%) of these patients had SAH centered in the quadrigeminal cistern without pretruncal blood, negative repeat angiograms, and an uncomplicated clinical course. CONCLUSION: Quadrigeminal SAH is a variant of PNSH that is not well described in the literature. It may comprise up to one-fifth of PNSH cases and carries a similar benign prognosis.

Aged↗

PubMed2000

Do reactive post-resection "injury" spikes exist?

PURPOSE: New post-resection spikes on electrocorticography (ECoG) after lesionectomy in patients with seizures may represent residual epileptogenic tissue or presumed reactive injury spikes. We investigated the existence of post-resection injury spikes by eliminating the possibility of residual epileptogenic tissue. METHODS: Preresection and post-resection ECoG was performed on seven patients with an intra-axial neocortical tumor (glioblastoma multiforme or metastasis) and no history of seizures. All tumors were gross-totally resected. RESULTS: The mean age of the patients was 59 years. The tumor location was frontal in four patients, parietal in two, and temporal in one. Two patients had preresection spikes with an average rate of 68 spikes/min that disappeared after surgery. Two different patients had new post-resection spikes, with an average firing rate of 4 spikes/min, despite normal preresection ECoG. In one of these patients, the new spikes were superimposed over a burst suppression pattern. Neither patient developed seizures after surgery. CONCLUSIONS: Surgical irritation of the neocortex is sufficient to produce reactive post-resection epileptogenic discharges surrounding an intra-axial neocortical tumor even in the absence of preoperative seizures and spikes. Injury spikes fire at a slow rate and are not predictive of clinical seizures.

Adult↗

PubMed2000

Asymmetry of neuronal activity during extracellular microelectrode recording from left and right human temporal lobe neocortex during rhyming and line-matching.

Recordings of neuronal activity in humans have identified few correlates of the known hemispheric asymmetries of functional lateralization. Here, we examine single-unit activity recorded from both hemispheres during two delayed match-to-sample tasks that show strong hemispheric lateralization based on lesion effects; a line-matching (LM) task related to the right hemisphere, and a rhyming (RHY) task related to the left. Nineteen neuronal populations were recorded with extracellular microelectrodes from the left temporal neocortex of 11 awake patients, and 18 from the right in 9 patients during anterior temporal lobectomy for complex partial seizures under local anesthesia. All subjects were left hemisphere dominant for language. Twelve (32%) populations exhibited statistically significant changes in activity at p <.05. Although changes in firing frequency were recorded from both hemispheres during both tasks, the RHY task elicited changes in activity several hundred milliseconds earlier on the left side than on the right. The LM task, on the other hand, induced changes earlier on the right side than on the left. Both hemispheres contained units active during verbal responses regardless of which behavior elicited the response. Our results indicate that cerebral dominance is reflected in earlier neuronal activity in the anterior temporal lobe during tasks lateralized to that hemisphere.

Adult↗

PubMed2000

Estrogen and progesterone receptor-negative T11 vertebral hemangioma presenting as a postpartum compression fracture: case report and management.

OBJECTIVE AND IMPORTANCE: Pregnancy-related vertebral hemangioma compressive myelopathy is a rare occurrence that tends to arise in the upper thoracic and lower cervical spine, peaks during the third trimester, and remits after parturition. Whether corticosteroid receptors play a role in the pathogenesis of these lesions is unknown. Most of these lesions have been managed with posterior decompression. CLINICAL PRESENTATION: A 29-year-old woman presented with acute-onset lower-extremity weakness and sensory loss immediately after parturition. INTERVENTION: We used a retropleural approach for anterior decompression and fusion, followed by radiation therapy. Immunohistochemical analysis of estrogen and progesterone receptor expression was performed. CONCLUSION: We report an unusual case of lower thoracic postpartum vertebral hemangioma compressive myelopathy caused by a parturition-related compression fracture. Results of tests for corticosteroid receptors were negative, which implicated a hemodynamic rather than hormonal cause for disease progression.

Adult↗

PubMed1999

Involvement of cajal-retzius neurons in spontaneous correlated activity of embryonic and postnatal layer 1 from wild-type and reeler mice.

Cajal-Retzius (CR) cells are a transient population of neurons in developing cortical layer 1 that secrete reelin, a protein necessary for cortical lamination. Combining calcium imaging of cortical hemispheres and cross-correlation analysis, we previously found spontaneous correlated activity among non-CR neurons in postnatal rat layer 1. This correlated activity was blocked by GABAergic and glutamatergic antagonists, and we postulated that it was controlled by CR cells. We now investigate the correlated activity of embryonic and postnatal layer 1 in wild-type and reeler mice, mutant in the production of reelin. We find that mouse layer 1 also sustains patterned spontaneous activity and that CR cells participate in correlated networks. These networks are present in embryonic marginal zone and are blocked by GABAergic and glutamatergic antagonists. Surprisingly, network activity in reeler mice displays similar characteristics and pharmacological profile as in wild-type mice, although small differences are detected. Our results demonstrate that the embryonic marginal zone has correlated spontaneous activity that could serve as the scaffold for the development of intracortical connections. Our data also suggest that reelin does not have a major impact in the development of specific synaptic circuits in layer 1.

Animals↗

PubMed1999

Supratentorial ependymomas in adult patients.

OBJECTIVE: Ependymomas arise from different areas in the neuraxis and have variable outcomes that depend on tumor location and patient age at the time of presentation. The predictive value of histology for these tumors is unresolved. We report a series of adult patients with supratentorial ependymomas to characterize the roles of surgery, histology, ploidy, and proliferation index in tumor control. METHODS: Fourteen of the 23 supratentorial ependymomas were in the region of the third ventricle and the remainder were located in the hemispheres. Resections were gross total in 12 patients, subtotal in 8, and biopsy in 3. A single pathologist reviewed all slides and quantitated the deoxyribonucleic acid. The mean follow-up duration was 95 months (+/-75 mo). RESULTS: All of the malignant ependymomas were hemispheric (n = 4). Mortality occurred only in patients with third ventricular tumors; two patients died as a result of surgical complications and three as a result of tumor progression. Kaplan-Meier estimates of 5- and 10-year survival rates were 100% for hemispheric and 72.5% for third ventricular tumors (62.5% including the two perioperative deaths). The median time to recurrence was 53 months, with a 10-year progression-free survival rate of 27%. Univariate analysis revealed that recurrence was associated with malignant histology, including mitoses, cellularity, and aneuploidy. For nonmalignant ependymomas, recurrence was associated with subtotal resection and metastases. S-phase fraction did not correlate with recurrence. Only malignant histology correlated with recurrence on multivariate analysis. CONCLUSION: Although the numbers are too small to draw any definite conclusions, treatment of ependymomas that arise in the supratentorial compartment in adult patients results in excellent outcomes despite frequent recurrences. Association with the third ventricle and metastases seem to have a negative impact on survival, whereas malignant histology, subtotal resection, and metastases may be predictors of recurrence.

Adolescent↗

PubMed1999

Function-specific high-probability "nodes" identified in posterior language cortex.

PURPOSE: Posterior, "Wenicke's," language areas have a high degree of between-subject variability, as shown by electrical-stimulation mapping. We investigated the possibility of an organized structure in the distribution of posterior language areas. METHODS: Extraoperative subdural grid stimulation was performed on 67 left hemisphere-dominant patients before resective epilepsy surgery during counting, naming, and reading. Intersubject-averaged language maps were generated in which stimulation disrupted only one language function and not the others, or combinations of language functions. RESULTS: Language sites, although highly variable between subjects, were not organized randomly and appeared to be arranged into several focal, non-contiguous, higher probability "nodes" devoted to different aspects of language processing. Speech-arrest sites were concentrated in classic Wernicke's area. Areas where stimulation induced only reading errors were found in the posterior middle temporal gyrus and the inferior parietal lobule. These regions may correspond with an orthographic input lexicon. Areas eliciting only naming errors were found in the posterior inferior temporal gyrus extending into the mid-middle temporal gyrus and may represent a visual-representation input lexicon. Sites where stimulation elicited errors in both naming and reading were more variable in location than sites devoted to only one function, extended farther anteriorly along the temporal neocortex, and may correspond with a semantic lexicon. CONCLUSIONS: The existence of high-probability nodes in posterior language cortex supports a modality-specific modular architecture and the possibility of a conserved, universal structure.

Adolescent↗

PubMed1999

Ventricular volume following third ventriculostomy.

OBJECT: Ventricular size often shows no obvious change following third ventriculostomy, particularly in the early postoperative period, making postoperative evaluation difficult without expensive and often invasive testing in patients with equivocal clinical responses. The authors hypothesized that performing careful volumetric measurements would show decreases in size within the first 3 weeks after surgery. METHODS: Volumetric measurements were calculated from standard 3 x 3-mm axial computerized tomography (CT) scans obtained immediately before and 3 and 21 days after surgery. Two independent investigators measured third ventricular volume in a series of 16 patients and lateral ventricular volume in 10 of the patients undergoing stereotactically guided endoscopic third ventriculostomy for noncommunicating hydrocephalus. Fifteen patients were symptomatically improved at the time the follow-up scan was obtained. Third ventricular volume decreased in all patients by a mean of 35% (range 7.8-95.1%) and lateral ventricular volume decreased in all patients by a mean of 33% (range 4.5-80.3%). The degree of change correlated with the length of preoperative symptoms (p < 0.005). The one patient who experienced no improvement showed no decrease in third ventricular volume. In seven of 10 patients, the decrease in third ventricular volume exceeded the decrease in lateral ventricular volume. Repeated measurements indicated that the 95% confidence interval for the authors' calculations varied around the mean by 2.5% for third ventricular volume and 1.2% for lateral ventricular volume. Long-term outcome was excellent, with only one case of delayed failure. The mean follow-up duration was 12 months. CONCLUSIONS: Volumetric measurements calculated from standard CT scans will show a demonstrable decrease in ventricular volume soon after successful third ventriculostomy and can be helpful in assessing patients postoperatively. Although the third ventricle may exhibit a greater decrease, the lateral ventricular measurements are more accurate. Patients with more indolent symptoms show the smallest change.

Adolescent↗

PubMed1998

Networks of coactive neurons in developing layer 1.

Spontaneous neuronal activity plays an important role in the development of cortical circuitry, yet its spatio-temporal dynamics are poorly understood. Cajal-Retzius (CR) neurons in developing layer 1 are necessary for correct cortical lamination and are strategically located to coordinate early circuit activity. To characterize the spontaneous activity of CR and other layer 1 neurons during cortical development, we imaged calcium transients in populations of layer 1 neurons in hemispheres and slices from postnatal rat somato-sensory neocortex. The spontaneous activity in layer 1 had complex spatio-temporal patterns. Groups of non-CR cells showed synchronous activations and formed networks of correlated neurons superimposed in the same territory. Correlated activity among non-CR cells was mediated by a depolarizing effect of GABA and was modulated by glutamate, probably released by CR cells. Our findings demonstrate that developing layer 1 can sustain complex patterns of correlated activity and reveal a circuit mechanism that can mediate this patterned activity.

Acetylcholine↗

PubMed1998

Functional magnetic resonance imaging localization of ictal onset to a dysplastic cleft with simultaneous sensorimotor mapping: intraoperative electrophysiological confirmation and postoperative follow-up: technical note.

INTRODUCTION: Although technically challenging to obtain, ictal functional magnetic resonance imaging has been used to localize ictal onset zones in a small number of patients. We used this technique to demonstrate the inherent epileptogenicity of dysplastic cortex. METHODS: We present a 16-year-old female patient with intractable left-sided sensorimotor seizures and a congenital dysplastic cleft lying along the right rolandic fissure. Preoperative functional magnetic resonance imaging (blood oxygen level-dependent sequence, 1.5 T) localized the motor and sensory cortices to the anterior border of the cleft. During a speech activation run, the patient experienced a 20-second seizure. Initial activation was seen within the dysplastic cortex along the deep posterior margin of the cleft. Intraoperative median nerve stimulation produced a distinct N20/P20 wave inversion over the dysplastic cleft. Stimulation mapping performed with the patient awake confirmed the location of the sensorimotor cortex on the anterior border of the cleft, and preresection electrocorticography identified abundant interictal spikes along the posterior border after opening the cleft. RESULTS: After surgical resection of the dysplastic cortex, the patient exhibited transient minimal weakness and mild neglect, which resolved within 1 week. Two years after surgery, she was neurologically intact and seizure-free. CONCLUSION: This study used functional magnetic resonance imaging to demonstrate the inherent epileptogenicity of dysplastic cortex and to simultaneously map ictal and functional cortex. The N20 wave inversion can be a useful intraoperative tool for identifying the central sulcus (or its equivalent), even in the presence of abnormal cortical architecture.

Adolescent↗

PubMed1998

Preoperative predictors of anterior temporal language areas.

OBJECT: Although it is known that 5 to 10% of patients have language areas anterior to the rolandic cortex, many surgeons still perform standard anterior temporal lobectomies for epilepsy of mesial onset and report minimal long-term dysphasia. The authors examined the importance of language mapping before anterior temporal lobectomy. METHODS: The authors mapped naming, reading, and speech arrest in a series of 67 patients via stimulation of long-term implanted subdural grids before resective epilepsy surgery and correlated the presence of language areas in the anterior temporal lobe with preoperative demographic and neuropsychometric data. Naming (p < 0.03) and reading (p < 0.05) errors were more common than speech arrest in patients undergoing surgery in the anterior temporal lobe. In the approximate region of a standard anterior temporal lobectomy, including 2.5 cm of the superior temporal gyrus and 4.5 cm of both the middle and inferior temporal gyrus, the authors identified language areas in 14.5% of patients tested. Between 1.5 and 3.5 cm from the temporal tip, patients who had seizure onset before 6 years of age had more naming (p < 0.02) and reading (p < 0.01) areas than those in whom seizure onset occurred after age 6 years. Patients with a verbal intelligence quotient (IQ) lower than 90 had more naming (p < 0.05) and reading (p < 0.02) areas than those with an IQ higher than 90. Finally, patients who were either left handed or right hemisphere memory dominant had more naming (p < 0.05) and reading (p < 0.02) areas than right-handed patients with bilateral or left hemisphere memory lateralization. Postoperative neuropsychometric testing showed a trend toward a greater decline in naming ability in patients who were least likely to have anterior language areas, that is, those with higher verbal IQ and later seizure onset. CONCLUSIONS: Preoperative identification of markers of left hemisphere damage, such as early seizure onset, poor verbal IQ, left handedness, and right hemisphere memory dominance should alert neurosurgeons to the possibility of encountering essential language areas in the anterior temporal lobe (1.5-3.5 cm from the temporal tip). Naming and reading tasks are required to identify these areas. Whether removal of these areas necessarily induces long-term impairment in verbal abilities is unknown; however, in patients with a low verbal IQ and early seizure onset, these areas appear to be less critical for language processing.

Adolescent↗

PubMed1997

Reading errors following right hemisphere injection of sodium amobarbital.

The role of the nondominant hemisphere in reading is controversial. We characterized the reading errors made by 64 right-handed adults with complex partial seizures (half with seizure foci on the right and half on the left), after right hemisphere injection of sodium amobarbital. Subjects were presented with 20 six-word sentences and all were found to have speech associated with the left hemisphere only. A variety of reading errors occurred, most of which fell under the syndrome of "neglect dyslexia" including deletions and substitutions of whole words on the left side of a line of text as well as within-word neglect errors. The nature of these errors indicated that they may have been caused by an interaction between a peripheral processing deficit and more centrally located conceptual knowledge of linguistic structure. Other errors could be attributed to a general decrease in attentional mechanisms. Neglect errors at the level of the sentence occurred in the absence of neglect errors at the level of the word although the converse was not true. This suggests that the latter may represent a more severe deficit in the mechanism that causes the former. A double dissociation existed between single word neglect dyslexia errors and "visual" errors, indicating separate processing mechanisms.

Adult↗

PubMed1997

The predictive value of intraoperative electrocorticography in resections for limbic epilepsy associated with mesial temporal sclerosis.

OBJECTIVE: Prior studies on the predictive value of intraoperative electrocorticography (ECoG) have been performed on heterogeneous groups of patients with both temporal and extratemporal interictal spikes, lesional and nonlesional pathological findings, and variably extensive resections by different surgeons. METHODS: We performed both pre- and postresection intraoperative ECoG on 29 consecutive patients with medial temporal lobe epilepsy (17 left-sided) who underwent standard nontailored resections by one surgeon (RRG). All patients had only temporal interictal spikes (six bitemporal) and mesial temporal sclerosis diagnosed by preoperative magnetic resonance imaging and confirmed by pathological examination of resected tissue. RESULTS: After a mean follow-up of 24.8 months, there were 15 (52%) patients who were seizure-free, 6 (21%) who were seizure-free except for auras, and 8 (28%) who had any seizure after the 1st postoperative month. Fourteen patients (48%) had active interictal discharges outside the area of planned resection revealed by preresection ECoG. Neither the presence of these spikes nor their mean frequency correlated with seizure outcome. Eleven patients (38%) had residual spike discharges after resection, and 18 patients (62%) had new spikes revealed by the postresection ECoG. Neither of these findings nor the mean spike frequency of residual or new spikes related to seizure outcome. Persistent spikes increased in frequency after resection in all outcome groups. CONCLUSIONS: Electrocorticographic monitoring of interictal epileptiform activity intraoperatively is not useful in the surgical treatment of patients undergoing standard resection for medial temporal lobe epilepsy with magnetic resonance imaging evidence of mesial temporal sclerosis.

Adolescent↗