Chronic subdural cortical stimulation for phantom limb pain: report of a series of two cases.

Phantom limb pain is a complex, incompletely understood pain syndrome that is characterized by chronic painful paresthesias in a previous amputated body part. Limited treatment modalities exist that provide meaningful relief, including pharmacological treatments and spinal cord stimulation that are rarely successful for refractory cases. Here, we describe our two-patient cohort with recalcitrant upper extremity phantom limb pain treated with chronic subdural cortical stimulation. The patient with evidence of cortical reorganization and almost 60 years of debilitating phantom limb pain experienced sustained analgesic relief at a follow-up period of 6 months. The second patient became tolerant to the stimulation and his pain returned to baseline at a 1-month follow-up. Our unique case series report adds to the growing body of literature suggesting critical appraisal before widespread implementation of cortical stimulation for phantom limb pain can be considered.

Subdural grid and depth electrode monitoring in pediatric patients.

Invasive electroencephalographic monitoring with implantable subdural electrodes and intraparenchymal depth electrodes has become a basic tenet of epilepsy surgery. Improved localization of epileptic foci justifies the secondary procedure and monitoring period in many patients. Informed use of invasive monitoring in conjunction with imaging and functional studies makes epilepsy surgery a smaller, safer, and more effective endeavor. Herein we review the history, indications, implementation, and foreseeable future of grid, strip, and depth electrode use.

Visual and semiautomated evaluation of epileptogenicity in focal cortical dysplasias - An intracranial EEG study.

INTRODUCTION: The aim of the study was the evaluation of the added value of depth to subdural electrodes in delineating epileptogenicity of focal cortical dysplasias (FCDs) and to test the Epileptogenicity Index (EI) in this setting. MATERIAL AND METHODS: Fifteen patients with FCD underwent iEEG with subdural and depth electrodes. Visual/EI analysis was performed in up to three habitual seizures per patient. RESULTS: Visual analysis: Grid onset seizures (n=10) started in electrodes overlying the lesion in 7 and remote from it in 3 cases. Depth onset seizures (n=7) affected only intralesional contacts in 4, intra- and extralesional in 2, and exclusively extralesional in 1 patient. Seizures started in depth and grid contacts simultaneously in 2 cases. EI analysis: The EI completely confirmed visual localization of seizure onset in 8 cases and depicted ictal onset-time accurately in 13. Beta/gamma ictal patterns were most reliably captured. Impact on surgical decision: Resection outline differed from MRI lesion in 7 patients based on grid and in three based on depth electrode information. DISCUSSION: In FCD, seizures can be generated within gyral/deep tissue appearing normal on imaging. CONCLUSION: Investigating FCD with subdural and depth electrodes is efficient to outline the seizure onset zone. The EI is a helpful additional tool to quantify epileptogenicity. Specific ictal patterns are prerequisite for reliable results.

Simultaneous subdural and scalp EEG correlates of frontal lobe epileptic sources.

OBJECTIVE: To assess the visibility and detectability in scalp electroencephalography (EEG) of cortical sources in frontal lobe epilepsy (FLE) as to their localization, and the extent and amplitude of activation. METHODS: We analyzed the simultaneous subdural and scalp interictal EEG recordings of 14 patients with refractory frontal lobe epilepsy (FLE) associated with focal cortical dysplasia. Subdural spike types were identified and averaged for source localization and detection of their scalp EEG correlates. Both raw and averaged scalp EEG segments were reviewed for spikes, blinded to subdural segments. We further analyzed the correlation of spike-to-background amplitude ratios in subdural and scalp EEG. RESULTS: We identified 36 spike types in subdural EEG, corresponding to 29 distinct sources. Four of 29 sources were visible by visual evaluation of scalp EEG and six additional sources were detectable after averaging: four in the medial frontal, two in the dorsolateral gyri, two in the depth of dorsolateral sulci, and two in the basal frontal region. Cortical sources generating scalp-detectable spikes presented a median of 6 cm(2) of activated cortical convexity surface and a subdural spike-to-background-amplitude ratio >8. These sources were associated with a higher number of activated subdural grid contacts and a higher subdural spike-to-background amplitude ratio than sources generating non-scalp-detectable spikes. SIGNIFICANCE: Not only dorsolateral but also basal and medial sources can be detectable in FLE. This is the first in vivo demonstration derived from simultaneous subdural and scalp EEG recordings of the complementary significance of extensive source activation and higher subdural spike-to-background amplitude ratio in the detection of cortical sources in FLE.

Placement of subdural grids in pediatric patients: technique and results.

PURPOSE: The purpose of this study is to describe common indications and technique for the application of chronic invasive electrodes in the pediatric patient suffering from medically intractable epilepsy. METHODS: This chapter was prepared based on a retrospective review of the literature and personal experience based from a large tertiary epilepsy center. CONCLUSIONS: Invasive subdural recordings are a safe and efficacious tool to identify the epileptogenic zone and its relationship to functional cortex in highly selected patients with medically refractory epilepsy. The ability to localize the EZ approaches 90 to 100 %, but seizure-free outcome is more complex depending greatly on the experience of the surgical team and the extent of resection.

Using subdural electrodes to assess the safety of resections.

Subdural electrodes are frequently used to aid in the neurophysiological assessment of patients with intractable seizures. We review their use for localizing cortical regions supporting movement, sensation, and language.

The impact of subdural air collection on intraoperative motor and somatosensory evoked potentials: fact or myth?

BACKGROUND: Surgery in the semi-sitting position is susceptible to changes in motor (MEP) and somatosensory evoked potentials (SEPs), which are not related to neurological impairment. These changes have been suggested to be caused by the insulating effect of subdural air collection. This study sought to investigate the correlation of MEP and SEP final-to-baseline amplitude ratios to postoperative volumetry of frontoparietal subdural air collection. METHODS: Median nerve SEP and hand MEP findings of 47 patients operated on in the semi-sitting position were compared with 7 patients operated on in the supine position. Computed tomography was routinely performed on the 1st postoperative day in all patients, and subdural air volumetry was calculated. Final-to-baseline MEP and SEP amplitude ratios were calculated and correlated to subdural air volumetry. FINDINGS: SEP changed in 12 patients, and MEP changed in 7 patients. Postoperative subdural air collections were significantly different between the groups (semi-sitting group, mean 31.2 cm(3); supine group, mean 2 cm3; p = 0.000). For the SEP ratios, a moderate negative correlation with subdural volumetry was found in the semi-sitting group (p = 0.044). Conversely, there was no correlation in the subset of patients with SEP attenuation (p = 0.846). As concerns the MEP ratios, no correlation was demonstrated in any group (semi-sitting, p = 0.967; supine, p = 0.193). CONCLUSIONS: Although SEP amplitude reductions were associated with large subdural air collections, this was not observed in the subset of patients with SEP attenuation and for the MEP monitoring, suggesting other pathophysiological mechanisms, such as brain shift, for the artificial amplitude reduction.

Extent of neocortical resection and surgical outcome of epilepsy: intracranial EEG analysis.

PURPOSE: Intracranial electroencephalography (EEG) monitoring is an important process in the presurgical evaluation for epilepsy surgery. The objective of this study was to identify the ideal resection margin in neocortical epilepsy guided by subdural electrodes. For this purpose, we investigated the relationship between the extent of resection guided by subdural electrodes and the outcome of epilepsy surgery. METHODS: Intracranial EEG studies were analyzed in 177 consecutive patients who had undergone resective epilepsy surgery. We reviewed various intracranial EEG findings and resection extent. We analyzed the relationships between the surgical outcomes and intracranial EEG factors: the frequency, morphology, and distribution of ictal-onset discharges, the propagation speed, and the time lag between clinical and intracranial ictal onset. We also investigated whether the extent of resection, including the area showing ictal rhythm and various interictal abnormalities--such as frequent interictal spikes, pathologic delta waves, and paroxysmal fast activity--influenced the surgical outcome. RESULTS: Seventy-five patients (42%) were seizure free. A seizure-free outcome was significantly associated with a resection that included the area showing ictal spreading rhythm during the first 3 s or included all the electrodes showing pathologic delta waves or frequent interictal spikes. However, subgroup analysis revealed that the extent of resection did not affect the surgical outcome in lateral temporal lobe epilepsy. CONCLUSIONS: The extent of resection is closely associated with surgical outcome, especially in extratemporal lobe epilepsy. Resection that includes the area with total pathologic delta waves and frequent interictal spikes predicts a good surgical outcome.

Rupture of middle fossa arachnoid cyst simulating new-onset migraine with aura.

Arachnoid cysts represent a common, innocent, finding in routine neuroimaging of headache patients. We present the first report of symptomatic migraine with aura caused by the spontaneous rupture of a middle fossa arachnoid cyst into the subdural space. Brain imaging enabled an accurate diagnosis and, subsequently, adequate surgical management.

Spontaneous acute spinal subdural hematoma: spontaneous recovery from severe paraparesis--case report and review.

Spontaneous idiopathic acute spinal subdural hematomas are highly exceptional. Neurological symptoms are usually severe, and rapid diagnosis with MRI is mandatory. Surgical evacuation has frequently been used therapeutically; however, spontaneous recovery in mild cases has also been reported. We present a case of spontaneous recovery from severe paraparesis after spontaneous acute SSDH, and review the English-speaking literature.

Chronic sub-dural hematomas: twist drill craniostomy with a closed system of drainage, for 48 hours only, is a valuable surgical treatment.

Twist drill craniostomy with closed drainage system for 48-hour duration is an effective treatment of chronic subdural hematomas.

Intradural spinal metastasis of renal cell cancer. Report of a case and review of 26 published cases.

Metastatic disease in the intradural compartment of the spine is a rare manifestation of cancer. We report the case of an 82-year-old patient with an intradural, extramedullary metastasis of renal cell carcinoma in the cervical spine. A literature search for intradural spinal metastases of renal cell carcinoma yielded a total of 26 further cases. 18 patients had sporadic renal cell carcinoma, and 9 patients had von Hippel-Lindau disease (VHL) in which the metastases of the renal cell carcinoma were embedded within spinal haemangioblastomas. Patients presented with paresis, back pain, altered sensation or, less frequently, bladder dysfunction. Intradural spinal metastases were diagnosed at an earlier age in VHL patients than in sporadic cases (mean 43 +/- 5 years vs. 60 +/- 14.5 years). The metastasis was surgically removed in 81% of patients. Pain improved in all patients, paresis in 90%, hypaesthesia in 38% and bladder dysfunction in 50%. Death occurred as a result of systemic cancer progression. 93% of patients in the sporadic renal cell cancer group died within 1.5 years, whereas two thirds of the VHL patients were alive after 2 years.

Disseminated intravascular coagulation after isolated mild head injury.

A rare case is described of acute disseminated intravascular coagulation (DIC) following isolated mild head injury with acute subdural haematoma, coagulopathy onset preceding craniotomy. Surgical treatment of the cause followed by swift diagnosis and treatment soon after surgery enabled a good outcome. Post-operative recollection of subdural and extadural blood was treated by further surgery. DIC following isolated mild head injury without axonal damage is rare, but fatal if missed. Thrombocytopaenia in head injured patients should be investigated expediently. Post-operative interim imaging (if not standard practice) should also be considered to exclude haemorrhagic recollection requiring further surgery.

Can subdural hematoma be a trigger for Guillain-Barré syndrome?

Guillain-Barré syndrome (GBS) is an acute inflammatory polyneuropathy which follows a precipitating event in approximately two thirds of cases. Although its pathogenesis is unclear, it is likely to be a consequence of an immune-mediated process. In the literature there are three case reports of GBS following subarachnoid hemorrhage, subdural hematoma, and facial bone fracture after head trauma.The unique feature of our case with GBS after subdural hematoma is the presence of cerebellar symptoms. We believe that GBS results from an aberrant immune response following trauma that somehow mistakenly attacks the nerve tissue of its host, and we discuss the effects of the trauma of head injury on cellular and humoral immunities and the absence of antiganglioside antibody (anti-GD1b IgG, which is accused of ataxia and cerebellar symptoms) in this case report.

Ictal onset patterns of subdural intracranial electroencephalogram in children: How helpful for predicting epilepsy surgery outcome?

AIMS: We aimed to classify ictal onset patterns (IOPs) in pediatric patients undergoing intracranial electroencephalography (IEEG) to guide surgery for refractory epilepsy. We aimed to determine if morphology of IOPs can predict surgical outcome. MATERIALS AND METHODS: We performed a retrospective review of pediatric patients who underwent epilepsy surgery guided by subdural IEEG from 2007 to 2016. IEEG seizures were reviewed by a blinded epileptologist. Data was collected on outcomes. RESULTS: Twenty-three patients with 784 seizures were included. Age at seizure onset was 0.2-11 (mean 4.3, standard deviation 3.2) years. Age at time of IEEG was 4-20 (mean 13.5, standard deviation 4.4) years. Five distinct IOPs were seen at seizure onset: A) Low voltage fast activity (LVFA) with spread to adjacent electrodes (n = 7 patients, 30%), B) Burst of LVFA followed by electrodecrement (n = 12 patients, 52%), C) Burst of rhythmic spike waves (RSW) followed by electrodecrement (n = 9 patients, 39%), D) RSW followed by LVFA (n = 7 patients, 30%), E) Rhythmic spikes alone (n = 10 patients, 43%). Twelve patients (52%) had the same IOP type with all seizures. When the area of the IOP was resected, 14 patients (61%) had Engel I outcomes. Patients who had LVFA seen within their predominant IOP type were more likely to have good surgical outcomes (odds ratio 7.50, 95% confidence interval 1.02-55.0, p = 0.05). Patients who had only one IOP type were more likely to have good outcomes than patients who had multiple IOP types (odds ratio 12.6, 95% confidence interval 1.19-134, p = 0.04). Patients who had LVFA in their predominant IOP type were older than patients who did not have LVFA (mean age 15.0 vs. 9.9 years, p = 0.02). CONCLUSIONS: LVFA at ictal onset and all seizures having the same IOP morphology are associated with increased likelihood of surgical success in children, but LVFA is less common in children who are younger at the time of IEEG.

Detection of temporal lobe spikes: comparing nasopharyngeal, cheek and anterior temporal electrodes to simultaneous subdural recordings.

OBJECTIVE: To compare nasopharyngeal (NP), cheek and anterior temporal (AT) electrodes for the detection yield and localization of interictal spikes in temporal lobe epilepsy. METHODS: In patients evaluated for epilepsy surgery with subdural electrocorticography electrodes, we simultaneously recorded NP, cheek and AT electrodes. Two observers identified spikes in EEG traces and marked in which channels they occurred. Interobserver agreement was calculated using Cohen's kappa. For localization, data-sets with high interobserver agreement (kappa-value 0.4) were evaluated. The subdural distribution of NP and AT spikes was mapped. RESULTS: Seven patients were included, six were analyzed for localization. Only 1.5% of spikes recorded by cheek electrodes were not seen on temporal leads, while 25% of NP spikes were not seen on either. Spikes only recorded by NP electrodes had mesiobasal, while AT spikes had lateral temporal distribution. CONCLUSIONS: NP electrodes can increase EEG spike detection rate in temporal lobe epilepsy and are more useful than cheek electrodes. Spikes that are seen only on NP electrodes tend to be mesiobasal temporal lobe spikes. SIGNIFICANCE: Adding NP electrodes to scalp EEG can aid interictal spike detection and source localization, especially in short recordings like MEG-EEG.

Spontaneous intracranial hypotension after labor without spinal intervention.

We present a 29-year-old woman admitted with severe postural headache after spontaneous term labor. Lactation ceased for the duration of headache. Magnetic resonance imaging (MRI) revealed dural thickening that is suggestive of spontaneous intracranial hypotension. CT-cisternography disclosed cervicodorsal dural leak. She was treated with a high-volume epidural blood patch (EBP) and her symptoms were relieved. Lactation returned to normal after EBP. She had normal findings on follow-up MRI examination at 6 months.

Subdural Tension on the Brain in Patients with Chronic Subdural Hematoma Is Related to Hemiparesis but Not to Headache or Recurrence.

BACKGROUND: Hemiparesis is a major symptom of chronic subdural hematoma (CSDH). Its severity does not always correlate with hematoma size. The authors analyzed hematoma thickness, pressure, and tension to clarify the mechanism of hemiparesis in CSDH patients. METHODS: A burr-hole surgery was performed on 124 CSDHs in 102 patients. Hematoma thickness and midline shift were measured by computed tomography, and hematoma pressure was measured in surgery. According to Laplace law, tension was calculated as follows: (half the hematoma thickness × hematoma pressure)/2. Student t test and Pearson correlation coefficient (r) were applied in statistical analysis of findings. RESULTS: Motor weakness was identified in 76.5% of our cases. Tension was strongly related to hemiparesis (r = -0.747, P < 0.01), whereas hematoma thickness (r = -0.458, P < 0.01) and pressure (r = -0.596, P < 0.01) were moderately correlated. Mean age of 14 patients (13.7%) with headache was much younger than those without headache (P < 0.01). Stronger midline shift (P < 0.01) and greater ratio of midline shift to hematoma thickness (P < 0.01) were statistically correlated with headache. Recurrence was recognized in 8 patients (7.8%), and stronger midline shift (P < 0.05) and greater ratio of midline shift to hematoma thickness (P < 0.05) were statistically associated with recurrence. CONCLUSIONS: Tension is the most influencing factor to hemiparesis in CSDH patients. This study also elucidates the mechanism for quick recovery from hemiparesis after surgery in that tension on the motor cortex is decreased immediately by drainage.

Papilledema as a manifestation of a spinal subdural abscess.

Papilledema is an uncommon presentation of spinal cord processes. Spinal subdural abscess (SSA) is a rare site of post-operative infection. We report a patient who developed papilledema as the primary manifestation of a post-operative lumbar subdural abscess. A spinal abscess should be considered in the post-operative spinal surgery patient who develops papilledema in the setting of persistent back pain. The increased intracranial pressure associated with lumbar spinal cord abscess most likely results from a markedly elevated cerebrospinal fluid (CSF) protein or the disruption of CSF flow in the spinal cul-de-sac.

Frequency domain analysis of human subdural recordings.

SUMMARY: It is possible to localize many aspects of cortical function and dysfunction without the use of direct electrical stimulation of cortex. This study explores the degree to which information can be obtained about functional cortical organization relative to epileptogenic regions through analysis of electrocorticographic recordings in the frequency domain. Information about the extent of seizure regions and the location of the normal sensory and motor homunculus and some higher language and memory related areas can be obtained through the analysis of task-related power spectrum changes and changes in lateral interelectrode coherence patterns calculated from interictal and ictal recordings.