Biomedical subjects

A G Parrent

Publications and source records attributed to A G Parrent.

13 recordsLinked to original sources

PubMed2000

Stereotactic surgery for temporal lobe epilepsy.

In light of the recent resurgence of interest in stereotactic functional procedures, the authors have reviewed the role of stereotactic ablative surgery in the treatment of temporal lobe epilepsy. Literature pertaining to stereotactic amygdalotomy, hippocampotomy and fornicotomy is reviewed and summarized. However, the results presented in those early studies are difficult to interpret given the surgical techniques and outcome assessment used. Modern stereotactic ablative surgery using current image-guided technology offers the opportunity to revisit some of these techniques. In recent studies of stereotactic amygdalohippocampotomy, outcomes are not as favorable as those obtained with standard temporal resections. However, these relatively discrete ablative techniques may shed light on the anatomical substrate underlying temporal lobe epilepsy.

Amygdala↗

PubMed2000

Cognitive outcome following pallidotomy: the influence of side of surgery and age of patient at disease onset.

OBJECT: The authors studied the neuropsychological correlates of stereotactically guided lesioning of the right and left posteroventral globus pallidus internus (GPi) in a prospective series of patients suffering from Parkinson's disease (PD). METHODS: Eighteen patients with PD who underwent stereotactically guided lesioning of the GPi (left side in 10 patients and right side in eight) completed neuropsychological evaluations before and after surgery. Patients served as their own controls. Multiple two-by-two repeated-measures analyses of variance were used to assess neuropsychological changes as a function of the side in which lesioning was performed (lesioning on the left side compared with that on the right) and surgery (presurgery compared with postsurgery). Relationships between cognitive variables and patient age at disease onset, age at surgery, and disease duration were examined using a linear regression model. The most striking findings were evident from results of a phonemic word fluency test in which patients in whom a left-sided pallidotomy had been performed achieved a mean performance score that was lower than the score of patients in whom a right-sided pallidotomy had been performed; this score declined even more as a result of surgery. Change in performance on the word fluency test across pre- and postoperative assessments was also related to patient age at onset of PD in those who had undergone left-sided pallidotomy, with patients of an older age at disease onset showing the greatest decline in performance. CONCLUSIONS: These preliminary findings indicate that the side on which surgery was performed and patient age at onset of PD are important in the prediction of postoperative cognitive outcome. The findings also indicate that stereotactically guided lesioning of the GPi presents a relatively mild cognitive risk.

Adult↗

PubMed2000

Endoscopically guided fenestration of the choroidal fissure for treatment of trapped temporal horn.

In recent years endoscopic procedures have been used more frequently to treat loculated hydrocephalus. The trapped temporal horn, a specific type of loculation, has traditionally been treated by means of ventricular shunt placement. By opening up loculations, however, this procedure can be simplified or, in some cases, even avoided. In this report the author discusses a case of trapped temporal horn that was caused by fungal meningitis and treated using endoscopically guided fenestration of the choroidal fissure, leading to clinical and radiographic resolution of the syndrome. Using this simple procedure allows the surgeon to take advantage of normal temporal horn anatomy and landmarks, avoiding the scarred and distorted region of ventricular obstruction.

Aged↗

PubMed1999

Stereotactic amygdalohippocampotomy for the treatment of medial temporal lobe epilepsy.

PURPOSE: This study was carried out to assess the safety and efficacy of stereotactic ablation of the amygdala and hippocampus for the treatment of medial temporal lobe epilepsy. METHODS: Twenty-two stereotactic amygdalohippocampotomies were performed in 19 patients with unilateral temporal lobe seizures by using magnetic resonance imaging (MRI) localization for target planning and radiofrequency techniques for lesion production. Seizure frequency was assessed at 3-monthly follow-up visits. Two lesion groups were defined. In group I, four to 11 (mean, 6.4) discrete lesions were made, encompassing the amygdala and anterior 13-21 mm (mean, 16.8 mm) of the hippocampus. In group II, a large number of confluent lesions were made (mean, 26.0; range, 12-54) encompassing the amygdala and anterior 15-34 mm (mean, 21.5 mm) of the hippocampus. MRI scanning was carried out 24 h and 6-9 months after surgery. RESULTS: In five group I patients, one (20%) experienced a favorable seizure outcome. Of 15 group II patients, one of whom had previously undergone limited lesioning and was also analyzed as part of group I, nine (60%) experienced a favorable seizure outcome, with two seizure free. MRI scans at 6- to 9-months' follow-up disclosed discrete areas of atrophy in the amygdala and hippocampus, interspersed with preserved brain in the group I patients. More uniform and complete destruction of amygdala and hippocampus was evident in group II patients. All lesions were confined to the amygdala and hippocampus, sparing the parahippocampal gyrus (PHG). CONCLUSIONS: The extensive amygdalohippocampal ablation in group II patients improved seizure outcome compared with more limited ablation in group I, but these results were not so good as those from temporal lobectomy in a similar patient group. When considered together with the results of selective amygdalohippocampectomy, and temporal resections that spare hippocampus or amygdala (all producing similar outcomes, and all involving resection of the entorhinal cortex), this study suggests a pivotal role of the entorhinal cortex in temporal epileptogenesis.

Adolescent↗

PubMed1999

Stereotactic radiofrequency ablation for the treatment of gelastic seizures associated with hypothalamic hamartoma. Case report.

The author presents the case of a patient with gelastic seizures associated with a hypothalamic hamartoma, in whom partial resection of the hamartoma followed by temporal lobectomy and orbitofrontal corticectomy failed to reduce the seizures. Subsequent stereotactic radiofrequency ablation of the hamartoma resulted in progressive improvement in the seizure disorder during a 28-month follow-up period. There is support in the literature for the concept that gelastic seizures originate directly from the hamartoma; however, direct surgical approaches to these lesions pose significant risks. It is proposed that the technique of radiofrequency ablation provides a minimally invasive, low-risk approach for the treatment of hypothalamic hamartomas.

Catheter Ablation↗

PubMed1998

MR in temporal lobe epilepsy: analysis with pathologic confirmation.

PURPOSE: We evaluated the MR findings in patients with temporal lobe epilepsy to determine the predictive value of MR imaging in assessing patient outcome. METHODS: MR studies from 186 of 274 consecutive patients who underwent temporal lobectomy for intractable epilepsy were reviewed retrospectively. Images were interpreted by an experienced neuroradiologist, who was blinded to the side of seizure activity and to pathologic findings. RESULTS: MR imaging exhibited 93% sensitivity and 83% specificity in detecting hippocampal/amygdalar abnormalities (n = 121), and 97% sensitivity and 97% specificity in detecting abnormalities in the rest of the temporal lobe (n = 60). Abnormal high signal of the hippocampus on T2-weighted images had a sensitivity of 93% and specificity of 74% in predicting mesial temporal sclerosis (n = 115). The presence of hippocampal atrophy on MR correlated with the duration of seizures. Sensitivity and specificity of MR imaging in detecting temporal lobe tumors (n = 42) were 83% and 97%, respectively, based on abnormal signal and mass effect. After surgery, 63% of patients were seizure free and 28% had a significant reduction of seizure frequency at an average of 24 months (range, 12 to 78 months) after surgery. Patients with a single lesion in the anterior temporal lobe or hippocampus/amygdala had a better outcome than patients with multiple lesions (n = 22). Interrater agreement varied from 0.4 to 0.93, with best agreement for tumors or abnormal hippocampal signal on T2-weighted images. CONCLUSION: MR imaging is highly sensitive in detecting and locating abnormalities in the temporal lobe and the hippocampus/amygdala in patients with temporal lobe epilepsy. Hippocampal atrophy appears to correspond to the duration of seizure disorder.

Adult↗

PubMed1997

Propofol sedation during awake craniotomy for seizures: electrocorticographic and epileptogenic effects.

This prospective study evaluated the effects of propofol sedation on the incidence of intraoperative seizures and the adequacy of electrocorticographic (ECoG) recordings during awake craniotomy performed for the management of refractory epilepsy. Thirty patients scheduled for temporal or frontal lobectomy for epilepsy under bupivacaine scalp block were randomized to receive patient-controlled propofol sedation (PCS) combined with a basal infusion of propofol (n = 15) or neurolept analgesia using an initial bolus dose of fentanyl (0.7 microg/kg) and droperidol (0.04 mg/kg) followed by a fentanyl infusion (n = 15). Propofol administration was suspended 15 min before ECoG recording in the PCS group. The occurrence of inappropriate intraoperative seizures was noted and, based on blind review, the adequacy of ECoG recordings was compared. A higher incidence of intraoperative seizures was noted among the neurolept patients (6 vs 0, P = 0.008). Intraoperatively, ECoG recordings were adequate to proceed with resection in both groups. Evidence of low spike activity on ECoG did not correlate with the type of sedation administered. Higher frequency background ECoG activity was noted among patients who received propofol, but this did not interfere with ECoG interpretation. The use of propofol sedation does not appear to interfere with ECoG during epilepsy surgery, provided administration is suspended at least 15 min before recording.

Adjuvants, Anesthesia↗

PubMed1997

Propofol sedation during awake craniotomy for seizures: patient-controlled administration versus neurolept analgesia.

This prospective study evaluated the safety and efficacy of patient-controlled sedation (PCS) using propofol during awake seizure surgery performed under bupivacaine scalp blocks. Thirty-seven patients were randomized to receive either propofol PCS combined with a basal infusion of propofol (n = 20) or neurolept analgesia using an initial bolus dose of fentanyl and droperidol followed by a fentanyl infusion (n = 17). Both groups received supplemental fentanyl and dimenhydrinate for intraoperative pain and nausea, respectively. Comparisons were made between groups for sedation, memory, and cognitive function, patient satisfaction, and incidence of complications. Levels of intraoperative sedation and patient satisfaction were similar between groups. Memory and cognitive function were well preserved in both groups. The incidence of transient episodes of ventilatory rate depression (<8 bpm) was more frequent among the propofol patients (5 vs 0, P = 0.04), particularly after supplemental doses of opioid. Intraoperative seizures were more common among the neurolept patients (7 vs 0, P = 0.002). PCS using propofol represents an effective alternative to neurolept analgesia during awake seizure surgery performed in a monitored care environment.

Adjuvants, Anesthesia↗

PubMed1997

Stereotactic amygdalohippocampotomy and mesial temporal spikes.

PURPOSE: To investigate the mechanism of mesial temporal spike generation, we sought to determine whether amygdalohippocampotomy by radiofrequency lesions altered spike rates in patients with medically intractable temporal lobe epilepsy. METHODS: The subjects were 14 patients whose ictal semiology, ictal and interictal EEGs, and neuropsychological profile were compatible with seizure origin from MRI-demonstrated unilateral mesial temporal sclerosis. Mesial temporal spikes were recorded by a multicontact electrode line stereotactically placed in the temporal horn of the lateral ventricle. A recording and lesioning electrode was also stereotactically advanced to multiple amygdala and hippocampal targets. Several confluent (9 patients) or discrete (5 patients) radiofrequency lesions were made in the amygdala and anterior hippocampus. Scalp and invasive recordings were performed before lesioning, between each lesioning process, and for 48 postoperative h. RESULTS: As compared to prelesion recordings, no consistent change in anterior and total mesial temporal spike rates occurred intraoperatively or postoperatively. Postlesion: prelesion spike ratios failed to correlate with effectiveness of lesionectomy for seizure control. In contrast, complex partial seizures improved in 13 of 14 patients. CONCLUSIONS: Amygdala and hippocampal destructive lesions had no consistent effect on meisal temporal spike quantity, but reduced temporal lobe CPS in 13 of 14 patients. This dichotomy suggests that CPS may result from concerted epileptogenesis of the hippocampus, entorhinal cortex, and possibly the amygdala, while the entorhinal cortex alone can produce interictal spikes.

Adolescent↗

PubMed1994

Complications of CT-guided stereotactic biopsy of intra-axial brain lesions.

A series of 300 consecutive stereotactic biopsies for intra-axial brain lesions performed by one neurosurgeon was critically analyzed regarding complications of the procedure. Complications were incurred by a total of 19 patients (6.3%). Five patients (1.7%) died following the procedure, all due to intracranial hypertension: one from subarachnoid hemorrhage, one from intracerebral hemorrhage, and three from increased edema without hemorrhage. The three patients who died without hemorrhage all had marked intracranial hypertension at the time of biopsy. All five patients who died harbored a glioblastoma multiforme. The surviving 14 patients (4.7%) with complications suffered increased neurological deficit due to hemorrhage. In 10 (3.3%), the deficit was mild and/or transient; in the other four (1.3%), a major deficit was incurred which markedly affected the remainder of the patient's life. Therefore, mortality or major morbidity was seen in 3.0% of patients and minor morbidity in 3.3%. Stereotactic biopsy is a very effective procedure with a complication rate significantly lower than that of craniotomy (particularly in the population of patients selected for stereotactic biopsy), but in a small number of patients the outcome is devastating.

Adolescent↗

PubMed1993

Tremor reduction by microinjection of lidocaine during stereotactic surgery.

We report our experience with lidocaine microinjection into the thalamus in 10 patients undergoing stereotactic thalamotomy for the treatment of Parkinsonian or non-Parkinsonian tremor. 18 injection sites in 4 patients with Parkinson's disease and 22 sites in 6 patients with other forms of tremor have been compared with respect to the effect of microstimulation. In over two thirds of cases the test microinjection replicated the effects of microstimulation. Long term follow up will be required to determine whether lesions made on the basis of lidocaine induced tremor suppression will result in a lower rate of tremor recurrence than those based on stimulation induced tremor suppression. In those patients in whom stimulation induced tremor suppression occurs but tremor arrest cannot be produced with lidocaine microinjection, chronic thalamic stimulation may be an alternative for the long term control of tremor in these patients.

Electric Stimulation Therapy↗

PubMed1993

Microinjection of lidocaine into human thalamus: a useful tool in stereotactic surgery.

A new method was developed to aid in the localization of the optimal site for a permanent lesion in movement disorder patients undergoing stereotactic thalamotomy. The method involved making small injections of a local anesthetic into the thalamus, which was also useful in assessing any possible side effects that could potentially arise from the lesion. Initial results indicate that 0.5 to 2-microliters injections of 2% lidocaine at appropriate sites in the thalamic ventrocaudal or ventrointermedius nucleus can produce a temporary marked suppression of tremor. In most cases the lidocaine induced effects mimicked those produced by high frequency electrical stimulation delivered to the same site. However, lidocaine had no effect at some sites where stimulation arrested tremor. This technique promises to be useful not only in the treatment of motor disorder patients but also in other cases where functional localization prior to lesioning is desirable.

Electric Stimulation↗

PubMed1992

Central pain in the absence of functional sensory thalamus.

Since the pioneering publication by Dejerine and Roussy, the thalamus has been commonly implicated in the pathogenesis of central pain. It is well known that cerebral lesions that spare the thalamus as well as both small and large ones within that structure produce similar pain syndromes, but could such pain develop if the thalamus were completely destroyed? CT scans of our patients suggested that it could. Moreover, exhaustive physiological explorations of the thalamus with macro- and microstimulation and microelectrode recordings in 2 more patients in whom CT scans suggested thalamic preservation despite massive suprathalamic infarcts, for the purpose of carrying out deep brain stimulation (DBS), revealed no evidence of ascending or descending diencephalic function. Their sensory examinations were similar to those of patients with congenital hemiatrophy who had undergone hemispherectomy. In 1 case, microstimulation of periaqueductal grey-periventricular grey (PAG-PVG) on the unaffected side of the brain induced the spectrum of responses correctly associated with these areas and during acute stimulation nearly abolished the patient's allodynia and hyperpathia. These observations suggest that processes occurring at a subdiencephalic level (or possibly ipsilaterally) may be involved in the generation of pain. Stroke-induced central pain remains a therapeutic dilemma for the pain surgeon, and the mechanisms underlying this pain state remain a mystery.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Arteries↗