Selective Posterior Cerebral Artery Wada Better Predicts Good Memory and Naming Outcomes Following Selective Stereotactic Thermal Ablation for Medial Temporal Lobe Epilepsy Than Internal Carotid Artery Wada.

The conventional intracarotid amobarbital (Wada) test has been used to assess memory function in patients being considered for temporal lobe epilepsy (TLE) surgery. Minimally invasive approaches that target the medial temporal lobe (MTL) and spare neocortex are increasingly used, but a knowledge gap remains in how to assess memory and language risk from these procedures. We retrospectively compared results of two versions of the Wada test, the intracarotid artery (ICA-Wada) and posterior cerebral artery (PCA-Wada) approaches, with respect to predicting subsequent memory and language outcomes, particularly after stereotactic laser amygdalohippocampotomy (SLAH). We included all patients being considered for SLAH who underwent both ICA-Wada and PCA-Wada at a single institution. Memory and confrontation naming assessments were conducted using standardized neuropsychological tests to assess pre- to post-surgical changes in cognitive performance. Of 13 patients who initially failed the ICA-Wada, only one patient subsequently failed the PCA-Wada (p=0.003, two-sided binomial test with p 0 =0.5) demonstrating that these tests assess different brain regions or networks. PCA-Wada had a high negative predictive value for the safety of SLAH, compared to ICA-Wada, as none of the patients who underwent SLAH after passing the PCA-Wada experienced catastrophic memory decline (0 of 9 subjects, p <.004, two-sided binomial test with p 0 =0.5), and all experienced a good cognitive outcome. In contrast, the single patient who received a left anterior temporal lobectomy after failed ICA- and passed PCA-Wada experienced a persistent, near catastrophic memory decline. On confrontation naming, few patients exhibited disturbance during the PCA-Wada. Following surgery, SLAH patients showed no naming decline, while open resection patients, whose surgeries all included ipsilateral temporal lobe neocortex, experienced significant naming difficulties (Fisher's exact test, p <.05). These findings demonstrate that (1) failing the ICA-Wada falsely predicts memory decline following SLAH, (2) PCA-Wada better predicts good memory outcomes of SLAH for MTLE, and (3) the MTL brain structures affected by both PCA-Wada and SLAH are not directly involved in language processing.

Radiofrequency Ablation Through Previously Effective Deep Brain Stimulation Leads for Parkinson Disease: A Retrospective Series.

BACKGROUND: Although deep brain stimulation (DBS) of the subthalamic nucleus (STN) or globus pallidus internus (GPi) is the surgical method of choice to treat the canonical symptoms of Parkinson disease, occasionally surgical sites become infected or the hardware erodes, necessitating explantation. Usual practice is to remove and reimplant replacement leads after tissue healing, leaving patients without the clinical benefits of DBS for several months, and at risk for DBS withdrawal in some, and some patients are no longer good surgical candidates for reimplantation. Radiofrequency ablation through the DBS lead is an option for these patients. METHODS: We performed a retrospective chart review of all patients who underwent radiofrequency ablation of the STN or GPi through indwelling DBS leads performed before hardware removal at our institution. We generated patient-specific anatomic models to determine lesion locations and volumes. RESULTS: Six patients underwent radiofrequency ablation of the STN (n = 4) and GPi (n = 2) through indwelling DBS leads. All 6 of these patients initially showed comparable motor symptom relief to that experienced with DBS before lesioning, with 4 patients sustaining meaningful long-term (≥2 years) improvement. Better outcomes were achieved in those patients with a higher percentage of the planned target lesioned. CONCLUSIONS: Radiofrequency ablation through indwelling DBS leads before explantation could be considered a viable alternative to subsequent reimplantation or stereotactic lesion in patients with Parkinson disease in whom hardware explantation is necessary, if the patient achieved substantive symptom relief with DBS. This approach avoids symptom exacerbation while awaiting revision surgery.

Spectral and Entropic Features Are Altered by Age in the Electroencephalogram in Patients under Sevoflurane Anesthesia.

BACKGROUND: Preexisting factors such as age and cognitive performance can influence the electroencephalogram (EEG) during general anesthesia. Specifically, spectral EEG power is lower in elderly, compared to younger, subjects. Here, the authors investigate age-related changes in EEG architecture in patients undergoing general anesthesia through a detailed examination of spectral and entropic measures. METHODS: The authors retrospectively studied 180 frontal EEG recordings from patients undergoing general anesthesia, induced with propofol/fentanyl and maintained by sevoflurane at the Waikato Hospital in Hamilton, New Zealand. The authors calculated power spectral density and normalized power spectral density, the entropic measures approximate and permutation entropy, as well as the beta ratio and spectral entropy as exemplary parameters used in current monitoring systems from segments of EEG obtained before the onset of surgery (i.e., with no noxious stimulation). RESULTS: The oldest quartile of patients had significantly lower 1/f characteristics (P < 0.001; area under the receiver operating characteristics curve, 0.84 [0.76 0.92]), indicative of a more uniform distribution of spectral power. Analysis of the normalized power spectral density revealed no significant impact of age on relative alpha (P = 0.693; area under the receiver operating characteristics curve, 0.52 [0.41 0.63]) and a significant but weak effect on relative beta power (P = 0.041; area under the receiver operating characteristics curve, 0.62 [0.52 0.73]). Using entropic parameters, the authors found a significant age-related change toward a more irregular and unpredictable EEG (permutation entropy: P < 0.001, area under the receiver operating characteristics curve, 0.81 [0.71 0.90]; approximate entropy: P < 0.001; area under the receiver operating characteristics curve, 0.76 [0.66 0.85]). With approximate entropy, the authors could also detect an age-induced change in alpha-band activity (P = 0.002; area under the receiver operating characteristics curve, 0.69 [0.60 78]). CONCLUSIONS: Like the sleep literature, spectral and entropic EEG features under general anesthesia change with age revealing a shift toward a faster, more irregular, oscillatory composition of the EEG in older patients. Age-related changes in neurophysiological activity may underlie these findings however the contribution of age-related changes in filtering properties or the signal to noise ratio must also be considered. Regardless, most current EEG technology used to guide anesthetic management focus on spectral features, and improvements to these devices might involve integration of entropic features of the raw EEG.

Safety and effectiveness of stereotactic laser ablation for epileptogenic cerebral cavernous malformations.

OBJECTIVE: Magnetic resonance (MR) thermography-guided laser interstitial thermal therapy, or stereotactic laser ablation (SLA), is a minimally invasive alternative to open surgery for focal epilepsy caused by cerebral cavernous malformations (CCMs). We examined the safety and effectiveness of SLA of epileptogenic CCMs. METHODS: We retrospectively analyzed 19 consecutive patients who presented with focal seizures associated with a CCM. Each patient underwent SLA of the CCM and adjacent cortex followed by standard clinical and imaging follow-up. RESULTS: All but one patient had chronic medically refractory epilepsy (median duration 8 years, range 0.5-52 years). Lesions were located in the temporal (13), frontal (five), and parietal (one) lobes. CCMs induced magnetic susceptibility artifacts during thermometry, but perilesional cortex was easily visualized. Fourteen of 17 patients (82%) with >12 months of follow-up achieved Engel class I outcomes, of which 10 (59%) were Engel class IA. Two patients who were not seizure-free from SLA alone became so following intracranial electrode-guided open resection. Delayed postsurgical imaging validated CCM involution (median 83% volume reduction) and ablation of surrounding cortex. Histopathologic examination of one previously ablated CCM following open surgery confirmed obliteration. SLA caused no detectable hemorrhages. Two symptomatic neurologic deficits (visual and motor) were predictable, and neither was permanently disabling. SIGNIFICANCE: In a consecutive retrospective series, MR thermography-guided SLA was an effective alternative to open surgery for epileptogenic CCM. The approach was free of hemorrhagic complications, and clinically significant neurologic deficits were predictable. SLA presents no barrier to subsequent open surgery when needed.

Stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy.

OBJECTIVE: To evaluate the outcomes 1 year and longer following stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy in a large series of patients treated over a 5-year period since introduction of this novel technique. METHODS: Surgical outcomes of a consecutive series of 58 patients with mesial temporal lobe epilepsy who underwent the surgery at our institution with at least 12 months of follow-up were retrospectively evaluated. A subgroup analysis was performed comparing patients with and without mesial temporal sclerosis. RESULTS: One year following stereotactic laser amygdalohippocampotomy, 53.4% (95% confidence interval [CI] = 40.8-65.7%) of all patients were free of disabling seizures (Engel I). Three of 9 patients became seizure-free following repeat ablation. Subgroup analysis showed that 60.5% (95% CI = 45.6-73.7%) of patients with mesial temporal sclerosis were free of disabling seizures as compared to 33.3% (95% CI = 15.0-58.5%) of patients without mesial temporal sclerosis. Quality of Life in Epilepsy-31 scores significantly improved at the group level, few procedure-related complications were observed, and verbal memory outcome was better than historical open resection data. INTERPRETATION: In an unselected consecutive series of patients, stereotactic laser amygdalohippocampotomy yielded seizure-free rates for patients with mesial temporal lobe epilepsy lower than, but comparable to, the outcomes typically associated with open temporal lobe surgery. Analogous to results from open surgery, patients without mesial temporal sclerosis fared less well. This novel procedure is an effective minimally invasive alternative to resective surgery. In the minority of patients not free of disabling seizures, laser ablation presents no barrier to additional open surgery. Ann Neurol 2018;83:575-587.