Keith W. MacDougall

Outcome of epilepsy surgery in patients investigated with subdural electrodes

Invasive intracranial electrodes (IE) are an important part of the work-up in many patients being considered for epilepsy surgery. Because IE are usually reserved for cases where seizure localization is ambiguous, one might expect that the eventual outcome of epilepsy surgery in these patients would be worse than in patients who did not require IE as part of their work-up. The purpose of this study was to specifically examine those patients who underwent insertion of subdural electrodes, to determine how many of these patients eventually underwent resective surgery of any type and to assess the eventual outcome. All cases admitted for subdural electrodes between January 2000 and June 2005 were reviewed. Surgical outcomes were reported using the Engel classification and a multivariate analysis was used to determine which factors were associated with successful surgery. 177 IE implantations were performed in 172 patients. Of these, 130 patients went on to have surgery. In the 113 of the 130 surgical patients in whom 1-year follow-up was available, 47% were seizure free at 1 year. Age was a major predictor of outcome with only 21% of patients over age 40 becoming seizure free with surgery compared to 58% in patients aged under 40 years (p=0.0004). Other predictors of an Engel I outcome included having a temporal lobectomy or supplementary motor area resection. Good results from eventual resective surgery can be achieved in patients needing invasive recordings. Younger patients with temporal lobe epilepsy seem to have the highest likelihood of seizure freedom.

Supplementary implantation of intracranial electrodes in the evaluation for epilepsy surgery

PURPOSE In some patients, resective epilepsy surgery can be planned based on a non-invasive work-up. However, in many cases, invasive monitoring with intracranial electrodes is required prior to recommending a resective procedure. Although the results of intracranial recordings are usually conclusive, a small group of patients may require additional electrodes to better define the seizure onset or propagation. METHODS One hundred and seventy seven patients who underwent intracranial electrode insertion between January 2000 and June 2005 were reviewed. Twelve of these patients required a supplementary implantation prior to making a recommendation about resective surgery. We report the nature of implantation as well as the outcomes in these 12 patients. RESULTS The mean age of these patients was 35 years (7 males). An average of 2.5 additional strip electrodes were required resulting in a mean of 9 strip type electrodes per patient, for a mean total of an additional 20 days. For most patients (9/12) this subsequent procedure identified an area of epileptic cortex other than that originally hypothesized. Seven patients went on to surgery of which three experienced a significant improvement in seizure control. CONCLUSIONS The addition of supplementary electrodes to an ongoing invasive electrode investigation can be a useful means of clarifying a patients suitability for a resective surgical procedure. While the surgical outcomes may not be as favorable as in patients in whom the investigations are simpler, a proportion of these patients do benefit from the eventual resective procedure. In cases where the supplementary electrodes lead to the conclusion that surgery is not indicated, these patients can be satisfied that the surgical option has been explored to the fullest extent possible.

Spontaneous Regression of an Intraparenchymal Cyst Following Deep Brain Stimulator Electrode Implantation: Case Report and Literature Review

BACKGROUND The development of an intraparenchymal cyst following deep brain stimulation (DBS) surgery is an uncommon complication that lacks a clearly defined management strategy. The pathophysiology is not known and may be related to perielectrode edema or cerebrospinal fluid tracking. Previous case reports have described various therapies for symptomatic cysts, including hardware removal or conservative treatment with steroids. CASE DESCRIPTION We present a male patient with bilateral DBS of the ventral intermediate nucleus of the thalamus for management of essential tremor, who developed a cystic cavitation at the left electrode tip and was followed without treatment. This patient developed dysarthria, gait impairment, and unilateral motor deficits 3 months after surgery. Perielectrode edema was initially identified, eventually coalescing into a cystic cavitation at the electrode tip. Cystic regression and symptomatic improvement were observed without any surgical or medical intervention, with full cyst resolution by 17 months. CONCLUSIONS Only 15 additional cases have been reported in the literature, although the true incidence may be underreported because of varying practices in obtaining postoperative scans. Cysts were identified in symptomatic patients on average 6.2 months after surgery. All symptomatic cysts were treated with hardware removal or steroid therapy. Observation alone may be sufficient when a DBS-associated cyst is identified. More reports are needed to characterize this rare complication.

Operative Nuances of Stereotactic Leksell Frame-Based Depth Electrode Implantation

Background For intracranial electroencephalographic monitoring, stereotactically implanted depth electrodes are increasingly used at epilepsy centers around the world. Objective To identify pearls and pitfalls from our experience with stereotactic Leksell (Elekta AB, Stockhom, Sweden) frame-based depth electrode implantation. Methods An intraoperative video of the implantation technique was recorded. Results A detailed description and a video on how to implant depth electrodes using the stereotactic Leksell frame is provided. Conclusion Neurosurgeons implanting depth electrodes for intracranial electroencephalographic monitoring might find the technical nuances and caveats described in this technical note useful for their practice.

Novel Connectivity Map Normalization Procedure for Improved Quantitative Investigation of Structural Thalamic Connectivity in Temporal Lobe Epilepsy Patients: Structural Parcellation of the Thalamus

Connectivity studies targeting the thalamus have revealed patterns of atrophy and deafferentiation in temporal lobe epilepsy (TLE). The thalamus can be parcellated using probabilistic tractography to demonstrate regions of cortical connectivity; however, sensitivity to smaller or less connected regions is low.

T05. Pre-surgical assessment of drug-resistant insular and peri insular epilepsy: A single center experience

Introduction Epilepsy arising from the insula is widely regarded as a challenging type of seizure, probably owing to the deep-seated location of the insula and the extensive connections it makes with adjacent structures. In recent years, we have rapidly gained insights into insular epilepsy-related obstacles. Here, we describe a detailed analysis of the electro-clinical manifestations of this type of epilepsy using intra-cerebral recordings performed with Stereo-electroencephalography (SEEG). Methods We retrospectively analyzed 12 patients from our epilepsy program who underwent insular exploration using SEEG between June 2013 and June 2017. Patient information reviewed included demographics, clinical history, neurological examination; neuroimaging studies (Brain MRI, PET, Ictal SPECT), Scalp video-EEG, intracranial recordings with SEEG, histopathological findings, and surgical outcomes. Results 12 patients (M:F = 4:8; mean age, 32.5 years; range, 19–60 years) were found with seizures originating from either the insula alone or simultaneously originating from the insula and adjacent structures. One patient had a family history of epilepsy and another one had previous exposure to viral meningoencephalitis. Six patients had undergone prior surgery for epilepsy treatment. The mean seizure frequency was 4 seizures per week, and one patient experienced seizures daily. The most common aura was somatosensory sensation, followed by cephalic sensation in 4 and 3 patients, respectively. The commonest type of seizure was focal with impaired awareness in 10 patients. 50% of the patients showed a tendency for secondary generalizations, and 25% showed nocturnal predominance. Lesions were observed on brain MRI in 8 cases. Scalp EEG revealed different interictal discharge distributions: 5 patients showed localized frontotemporal spikes, 3 showed bilateral temporal spikes, and no spikes were detected in 4. The location of ictal onset could be localized in only 50% of patients. The most common scalp EEG ictal pattern was rhythmic delta activity (1–3 Hz). Subsequent SEEG showed six patients found to have a combination of clinical and subclinical seizures. SEEG clinical seizure onset from the insula alone was found in 50% of the patients (3 right, 2 left, 1 bilateral). The other patients presented with simultaneous onset from the insula and adjacent structures: 4 from mesial temporal structures, 1 temporal operculum, and 1 frontal operculum. The commonest SEEG ictal pattern was low voltage fast activity in 8 patients. Surgical resections guided by SEEG findings were performed in 5 patients and led to excellent outcomes; all these cases had Engle class 1 outcome at 6–24 months follow up. Conclusion We observed that it is not uncommon for seizures to simultaneously originate from the insula and adjacent structures. However, non-invasive EEG monitoring tools are likely insufficient to detect such simultaneous seizures. For the given sample, SEEG proved beneficial in providing optimal surgical outcomes.

Intracranial Electroencephalographic Monitoring: From Subdural to Depth Electrodes.

At the London Health Sciences Centre Epilepsy Program, stereotactically implanted depth electrodes have largely replaced subdural electrodes in the presurgical investigation of patients with drug-resistant epilepsy over the past 4 years. The rationale for this paradigm shift was more experience with, and improved surgical techniques for, stereoelectroencephalography, a possible lower-risk profile for depth electrodes, better patient tolerability, shorter operative time, as well as increased recognition of potential surgical targets that are not accessible to subdural electrodes.

Cervical Spinal Cord and Dorsal Nerve Root Stimulation for Neuropathic Upper Limb Pain.

BACKGROUND Spinal cord stimulation (SCS) is a well-established treatment for chronic neuropathic pain in the lower limbs. Upper limb pain comprises a significant proportion of neuropathic pain patients, but is often difficult to target specifically and consistently with paresthesias. We hypothesized that the use of dorsal nerve root stimulation (DNRS), as an option along with SCS, would help us better relieve pain in these patients. METHODS All 35 patients trialed with spinal stimulation for upper limb pain between July 1, 2011, and October 31, 2013, were included. We performed permanent implantation in 23/35 patients based on a visual analogue scale pain score decrease of ≥50% during trial stimulation. RESULTS Both the SCS and DNRS groups had significant improvements in average visual analogue scale pain scores at 12 months compared with baseline, and the majority of patients in both groups obtained ≥50% pain relief. The majority of patients in both groups were able to reduce their opioid use, and on average had improvements in Short Form-36 quality of life scores. Complication rates did not differ significantly between the two groups. CONCLUSIONS Treatment with SCS or DNRS provides meaningful long-term relief of chronic neuropathic pain in the upper limbs.

New-Onset Stutter After Electrode Insertion in the Ventrocaudalis Nucleus for Face Pain

BACKGROUND Deep brain stimulation (DBS) of the ventrocaudalis nucleus of the thalamus is a last resort treatment for chronic refractory pain. DBS is generally a safe procedure, although it can result in functional disturbances depending on the site of stimulation. There has been 1 previous report of stuttering induced by microlesioning of the thalamus, as well as several reports of stuttering induced by stimulation of the thalamus and other related structures in the brain. CASE DESCRIPTION We describe the case of a patient with trigeminal deafferentation face pain who was treated with DBS of the ventrocaudalis nucleus thalamus and developed a reversible stutter immediately on insertion of the electrode. The stutter improved significantly over 12 days after implant; however, the device was not effective in relieving the patients pain and was removed. CONCLUSIONS Stuttering is a rare complication of deep brain exploration of the sensory thalamus. Our coordinates are near to but in a distinct anatomic region compared with cases previously described as having similar effects on speech.

Subdural hematoma: a rare presentation of a convexity meningioma.

A 69-year-old male presented to a peripheral emergency department with a several day history of increasing confusion and headache. On admission, his Glasgow Coma Scale (GCS) score was 10 (E3 M6 V1). He was mute but would obey commands intermittently. Cranial nerve exam was normal and there was no evidence of weakness. A computed tomogram (CT) head (Figure 1) showed a chronic subdural hematoma with midline shift, as well as a mass within the left frontal region that appeared consistent with a convexity meningioma seen on magnetic resonance imaging (MRI) two years prior (Figure 2). The patient was not on any blood thinners and had no history of falls. Past medical history also included hypertension and prostate cancer.