Reducing morbidity associated with subdural drain placement after burr-hole drainage of unilateral chronic subdural hematomas: a retrospective series comparing conventional and modified Nelaton catheter techniques.

PURPOSE: Placement of a subdural drain after burr-hole drainage of chronic subdural hematoma (cSDH) significantly reduces risk of its recurrence and lowers mortality at 6 months. Nonetheless, measures to reduce morbidity related to drain placement are rarely addressed in the literature. Toward reducing drain-related morbidity, we compare outcomes achieved by conventional insertion and our proposed modification. METHODS: In this retrospective series from two institutions, 362 patients underwent burr-hole drainage of unilateral cSDH with subsequent subdural drain insertion by conventional technique or modified Nelaton catheter (NC) technique. Primary endpoints were iatrogenic brain contusion or new neurological deficit. Secondary endpoints were drain misplacement, indication for computed tomography (CT) scan, re-operation for hematoma recurrence, and favorable Glasgow Outcome Scale (GOS) score (≥ 4) at final follow-up. RESULTS: The 362 patients (63.8% male) in our final analysis included drains inserted in 56 patients by NC and 306 patients by conventional technique. Brain contusions or new neurological deficits occurred significantly less often in the NC (1.8%) than conventional group (10.5%) (P = .041). Compared with the conventional group, the NC group had no drain misplacement (3.6% versus 0%; P = .23) and significantly fewer non-routine CT imaging related to symptoms (36.5% versus 5.4%; P < .001). Re-operation rates and favorable GOS scores were comparable between groups. CONCLUSION: We propose the NC technique as an easy-to-use measure for accurate drain positioning within the subdural space that may yield meaningful benefits for patients undergoing treatment for cSDH and vulnerable to complication risks.

Mapping and monitoring of brainstem surgery.

The surgical morbidity of brainstem lesions is higher than in other areas of the central nervous system because the compact brainstem is highly concentrated with neural structures that are often distorted or even unrecognizable under microscopic view. Intraoperative neurophysiologic mapping helps identify critical neural structures to avoid damaging them. With the trans-fourth ventricular floor approach, identifying the facial colliculi and vagal and hypoglossal triangles enables incising and approaching the brainstem through the safe entry zones, the suprafacial or infrafacial triangle, with minimal injury. Corticospinal tract mapping is adopted in the case of brainstem surgery adjacent to the corticospinal tract. Intraoperative neurophysiologic monitoring techniques include motor evoked potentials (MEPs), corticobulbar MEPs, brainstem auditory evoked potentials, and somatosensory evoked potentials. These provide real-time feedback about the functional integrity of neural pathways, and the surgical team can reconsider and correct the surgical strategy accordingly. With multimodal mapping and monitoring, the brainstem is no longer "no man's land," and brainstem lesions can be treated surgically without formidable morbidity and mortality.

Intraoperative neurophysiology in intramedullary spinal cord tumor surgery.

Intramedullary spinal cord tumor (ISCT) surgery is challenged by a significant risk of neurological injury. Indeed, while most ISCT patients arrive to surgery in good neurological condition due to early diagnosis, many experience some degree of postoperative sensorimotor deficit. Thus, intraoperative neuromonitoring (IONM) is invaluable for providing functional information that helps neurosurgeons tailor the surgical strategy to maximize resection while minimizing morbidity. Somatosensory evoked potential (SEP), muscle motor evoked potential (mMEP), and D-wave monitoring are routinely used to continuously assess the functional integrity of the long pathways within the spinal cord. More recently, mapping techniques have been introduced to identify the dorsal columns and the corticospinal tracts. Intraoperative SEP decline is not a sufficient reason to abandon surgery, since SEPs are very sensitive to anesthesia and surgical maneuvers. Yet, a severe proprioceptive deficit may adversely impact daily life, and the value of SEPs should be reconsidered. While mMEPs are good predictors of short-term motor outcome, the D-wave is the strongest predictor of long-term motor outcome, and its preservation during surgery is essential. Mapping techniques are promising but still need validation in large cohorts of patients to determine their impact on clinical outcome. The therapeutic rather than merely diagnostic value of IONM in spine surgery is still debated, but there is emerging evidence that IONM provides an essential adjunct in ISCT surgery.

Monitoring spinal surgery for extramedullary tumors and fractures.

Meningiomas are the most common intradural extramedullary tumors, followed by nerve sheath tumors that can also grow extradurally. Metastases are the most frequent extradural tumors and most commonly affect the thoracic vertebrae. Spinal fractures with column dislocation and/or instability require surgical fixation. Spine surgery for an extramedullary tumor or fracture usually involves decompression of neural elements and instrumentation for stabilization. These procedures risk spinal cord and nerve root injury. The incidence of nerve root deficits after resection of nerve sheath tumors is particularly high since the tumor grows from the rootlets. Intraoperative neurophysiologic monitoring and mapping techniques have been introduced to prevent iatrogenic neurologic deficits. These include motor and sensory evoked potentials, electromyography, compound muscle action potentials, and the bulbocavernosus reflex. The combination of techniques chosen for a particular procedure depends on the surgical level and the character of the lesion.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Intraoperative identification of the corticospinal tract and dorsal column of the spinal cord by electrical stimulation.

OBJECTIVES: Anatomical identification of the corticospinal tract (CT) and the dorsal column (DC) of the exposed spinal cord is difficult when anatomical landmarks are distorted by tumour growth. Neurophysiological identification is complicated by the fact that direct stimulation of the DC may result in muscle motor responses due to the centrally activated H-reflex. This study aims to provide a technique for intraoperative neurophysiological differentiation between CT and DC in the exposed spinal cord. METHODS: Recordings were obtained from 32 consecutive patients undergoing spinal cord tumour surgery from July 2015 to March 2017. A double train stimulation paradigm with an intertrain interval of 60 ms was devised with recording of responses from limb muscles. RESULTS: In non-spastic patients (55% of cohort) an identical second response was noted following the first CT response, but the second response was absent after DC stimulation. In patients with pre-existing spasticity (45%), CT stimulation again resulted in two identical responses, whereas DC stimulation generated a second response that differed substantially from the first one. The recovery times of interneurons in the spinal cord grey matter were much shorter for the CT than those for the DC. Therefore, when a second stimulus train was applied 60 ms after the first, the CT-fibre interneurons had already recovered ready to generate a second response, whereas the DC interneurons were still in the refractory period. CONCLUSIONS: Mapping of the spinal cord using double train stimulation allows neurophysiological distinction of CT from DC pathways during spinal cord surgery in patients with and without pre-existing spasticity.

Extended exposure of the petroclival junction: The combined anterior transpetrosal and subtemporal/transcavernous approach.

BACKGROUND: The combined anterior transpetrosal and subtemporal/transcavernous (atsta) approach to the petroclival junction provides a wide exposure facilitating resection of large tumor lesions such as petroclival mengiomas, chondrosarcomas, or chordomas. In this article we provide technical instructions on the approach with anatomical consideration and a literature review of previous applications of this approach. METHODS: The combined approach was performed in two cadaveric specimen and relevant anatomical aspects were studied. Additionally, the authors performed a review of the literature focusing on indications, neurologic outcome, and complications associated with the technique. RESULTS: A combined atsta approach offers a wide exposure of the crus cerebrum, pons, basal temporal lobe, cranial nerves III to VII/VIII, posterior cerebral artery (PCA), superior cerebellar artery (SCA), basilar artery (BA), anterior inferior cerebellar artery (AICA), and posterior communicating artery (Pcom). It has been successfully applied with acceptable morbidity and mortality rates, mainly for (spheno-) petroclival meningiomas. CONCLUSION: The combined approach studied here is a useful skull base approach to the petroclival junction and can be applied to treat large or complex pathologies of the region. Detailed anatomical knowledge is essential.

The Interpretation of Muscle Motor Evoked Potentials for Spinal Cord Monitoring.

OBJECTIVE: To provide a summary of the intraoperative monitoring of muscle motor evoked potentials (MEPs) based on the presence-absence concept during neurosurgical operations along the spinal cord. METHOD: Expert review. DISCUSSION: The measurable parameters of MEPs, such as signal amplitudes and thresholds vary considerably both during a single surgery in a single individual patient as well as between individuals and operations. The presence or absence of responses irrespective of stimulus intensity and response amplitude is much more clearly defined. The correlation of intraoperative MEP data to clinical findings preoperatively and postoperatively so far is best if a presence-absence paradigm is used. The most reliable correlation of postoperative motor deficits is with the disappearance of previously present MEPs, not with the deterioration of amplitudes or the elevation of thresholds. However, in intraoperative decision making an elevation of threshold, without signal loss may still be considered a practical warning sign as it may be a subclinical injury indicator, and may therefore induce a change in surgical strategy. This may be considered a minor warning criterion. A practical concept of the combined use of MEPs with D-wave recordings produced a neurophysiological pattern, which correlates with a reversible motor deficit: Disappearance of MEPs correlates with transient motor deficits if the D-wave amplitude is preserved above an approximate value of 50% of its baseline. Disappearance of the D-wave correlates to paraplegia. CONCLUSIONS: To date, the best correlation of muscle MEP data to clinical deficits lies in the assessment of disappearance of a previously present MEP regardless of thresholds or amplitudes. Increase in stimulus thresholds for MEPs or to a lesser degree decrement of signal amplitudes may be considered subclinical injury indicators without correlation to neurological dysfunction and thus is considered a minor warning criterion.

Intracranial Interdigitating Dendritic Cell Sarcoma: First Case Report.

BACKGROUND AND IMPORTANCE: This is the first report of a primarily intracranial interdigitating dendritic cell sarcoma (IDCS). CLINICAL PRESENTATION: A 39-year-old patient with right hemiparesis underwent complete resection of a large parafalcine tumor with subsequent complete recovery of neurological symptoms. Histologically, the tumor was diagnosed as IDCS. Extensive staging did not reveal any extracranial manifestation of this disease. After 1.5 years, the patient remains recurrence free and is being observed closely. CONCLUSION: IDCS are exceedingly rare tumors and so far have not been found intracranially. On the basis of the limited experience with extracranial occurrence, this tumor is best managed by complete resection and careful oncological observation. ABBREVIATIONS: FDCS, follicular dendritic cell sarcomaIDCS, interdigitating dendritic cell sarcomaRTU, ready-to-use kit.

Intrathecal morphine analgesia after cervical and thoracic spinal cord tumor surgery.

OBJECT: The aim of this study was to provide evidence for the effect of intrathecal morphine application after spinal cord tumor resection. METHODS: Twenty patients participated in a prospective open proof-of-concept study. During dural closure, morphine (7 µg/kg) was injected into the subarachnoid space. All patients were monitored in an intensive care setting postoperatively. Pain, additional opioids given, and vital parameters were recorded. RESULTS: Six patients received a mean morphine dose of 365 µg between C-3 and C-7 and 14 patients received a mean dose of 436 µg between T-2 and T-12. In the cervical and thoracic groups, the mean Numeric Rating Scale score was highest upon intensive care unit admission (1.2 and 2.5, respectively) and declined at 12 hours (0.5 and 0.8, respectively). Minimal extra morphine was required. Minor side effects occurred without consequence. CONCLUSIONS: Intrathecal morphine for postoperative analgesia after resection of cervical and thoracic spinal cord tumors is effective and safe. These preliminary results require confirmation by larger comparative studies and further clinical experience.

Quality of life after surgical treatment of primary intramedullary spinal cord tumors in children.

OBJECT: Presently, the best available treatment for intramedullary spinal cord tumors (IMSCTs) in children is microsurgery with the objective of maximal tumor removal and minimal neurological morbidity. The latter has become manageable with the development and standard use of intraoperative neurophysiological monitoring. Traditionally, the perioperative neurological evaluation is based on surgical or spinal cord injury scores focusing on sensorimotor function. Little is known about the quality of life after such operations; therefore, this study was designed to investigate the impact of surgery for IMSCTs on the quality of life in children. METHODS: Twelve consecutive pediatric patients treated for IMSCT were included in this retrospective fixed cohort study. A multidimensional questionnaire-based quality of life instrument, the Pediatric Quality of Life Questionnaire version 4 (PedsQL 4.0), was chosen to analyze follow-up data. This validated instrument particularly allows for a comparison between a patient cohort and a healthy pediatric sample population. RESULTS: Of 11 mailed questionnaires (1 patient had died of progressive disease), 10 were returned, resulting in a response rate of 91%. There were 8 low-grade lesions (5 pilocytic astrocytomas, 1 ganglioglioma, 1 hemangioblastoma, and 1 cavernoma) and 4 high-grade lesions (2 anaplastic gangliogliomas, 1 glioblastoma, and 1 glioneuronal tumor). The mean age at diagnosis was 7.5 years, the mean follow-up was 4.2 years, and 83% of the patients were male. Total resection was achieved in 5 patients and subtotal resection in 7. Four patients had undergone 2 or more resections. The 4 patients with high-grade tumors and 2 with incompletely resected low-grade tumors underwent adjuvant treatment (2 chemotherapy and 4 both radiotherapy and chemotherapy). The mean modified McCormick Scale score at the time of diagnosis was 1.7; at the time of follow-up, 1.5. The mean PedsQL 4.0 total score in the low-grade group was 78.5; in the high-grade group, 82.6. There was no significant difference in PedsQL 4.0 scores between the patient cohort and the normal population. CONCLUSIONS: In a small cohort of children who had undergone surgery for IMSCTs with a mean follow-up of 4.2 years, quality of life scores according to the PedsQL 4.0 instrument were not different from those in a normal sample population.

Pituitary surgery: experience from a large network in Central Switzerland.

PRINCIPLES: During the past years our group built a care network for patients with pituitary tumours with referrals from the midlands and the central part of Switzerland, comprising about 1.6 million inhabitants. The purpose of this retrospective observational study with longitudinal data is to review the experience of pituitary surgery and the operative outcome within this Swiss-wide largest network. METHODS: A total of 182 patients operated at the Neurosurgical Department of the Kantonsspital Aarau 2005-2010 were included in this study. The follow-up was 3.6±1.6 years. RESULTS: The following lesions were found: non-functioning adenoma (n = 114; 63%); macroprolactinoma (n = 18; 10%); microprolactinoma (n = 11; 6%); acromegaly (n = 11; 6%), Cushing's disease (n = 7; 4%); Rathke's cleft cyst (RCC; n = 9; 5%); others (n = 12; 7%). Intraoperative MRI (iMRI) was used in 115 (63%) patients. Preoperatively, hypopituitarism was found in 105 (58%) patients. Postoperative recovery of defunct axes was detected in 48%. Visual field and visual acuity deficits due to optic pathway compression by tumour were detected in 48% and 41% of the patients, respectively. Postoperative recovery of visual function was seen in 89%. The increase of total resection rate by iMRI was statistically significant (p = 0.0007). Recurrent tumour growth was seen in 5 (3%) patients during follow-up. CONCLUSIONS: Transsphenoidal surgery is the primary treatment for most sellar lesions. The use of iMRI may lead to higher gross total resection rates. In Switzerland close cooperation between specialised centres is a very positive experience both to support operative case loads and to optimise patient follow-up.

Anaplastic ganglioglioma: a very rare intramedullary spinal cord tumor.

Gangliogliomas (GGs) are a small subset of intramedullary spinal cord tumors in children. The anaplastic variant (WHO grade III) appears to be an extreme rarity. A literature research revealed only 15 case reports of intramedullary anaplastic GGs (aGGs) and only 4 pediatric patients. The course of an 18-month-old boy with sudden onset of paraparesis is presented. Spinal MRI revealed a contrast-enhancing intramedullary tumor ranging from T6 to T12. The patient underwent a standard laminectomy/laminoplasty and gross total resection of the lesion. His neurological status remained unchanged postoperatively and he recovered very well during outpatient neurorehabilitation. Neuropathologic examination revealed an aGG of WHO grade III. Because of the high-grade histology, adjuvant radiotherapy and chemotherapy with temozolomide were administered. The patient subsequently recovered to a normal functional status. Clinical and radiographic progression-free survival is now 4 years. Based on an extensive literature review, this is only the fifth pediatric patient with a primary intramedullary aGG and the second with documented progression-free survival of over 4 years. Another 4 primary intramedullary aGGs in adults and 7 patients with spinal dissemination from a cerebral aGG or malignant transformation of a low-grade GG have been reported. In comparison to the published case reports, which often indicate significant neurological dysfunction and rather short survival, the neurological recovery in this patient was favorable, and the oncologic outcome even more so. This is an argument for the use of the aggressive treatment regimen of complete resection followed by radio- and chemotherapy applied here.

Intraoperative neurophysiology of the conus medullaris and cauda equina.

PURPOSE: Intraoperative neurophysiological techniques are becoming routine tools for neurosurgical practice. Procedures affecting the lumbosacral nervous system are frequent in adult and pediatric neurosurgery. This review provides an overview of the techniques utilized in cauda and conus operations. METHODS: Two basic methodologies of intraoperative neurophysiological testing are utilized during surgery in the lumbosacral spinal canal. Mapping techniques help identify functional neural structures, namely, nerve roots and their respective spinal levels. Monitoring is referred to as the technology to continuously assess the functional integrity of pathways and reflex circuits. For mapping direct electrical stimulation of a structure within the surgical field and recording at a distant site, usually a muscle is the most commonly used setup. Sensory nerve roots or spinal cord areas can be mapped by stimulation of a distant sensory nerve or skin area and recording from a structure within the surgical field. Continuous monitoring of the motor system is done with motor evoked potentials. These are evoked by transcranial electrical stimulation and recorded from lower extremity and sphincter muscles. Presence or absence of muscle responses are the monitored parameters. To monitor the sensory pathways, sensory potentials evoked by tibial, peroneal, or pudendal nerve stimulation and recorded from the dorsal columns with a spinal electrode or as cortical responses from scalp electrodes are used. Amplitudes and latencies of these responses are measured for interpretation. The bulbocavernosus reflex, with stimulation of the pudendal nerve and recording from the external anal sphincter, is used for continuous monitoring of the reflex circuitry. The presence of absence of this response is the pertinent parameter monitored. Stimulation of individual dorsal nerve roots is used to identify those segments that generate spastic activity and which may be cut during selective dorsal rhizotomy. Electromyographic activity can be continuously observed during surgery, and monitoring concepts developed in cranial nerve surgery may be used in the cauda equina as well. CONCLUSION: A range of intraoperative neurophysiological techniques are available for neurophysiological testing of the neural structures of conus medullaris and cauda equina.

The evolution of intramedullary spinal cord tumor surgery.

OBJECTIVE: Resections of intramedullary spinal cord tumors were attempted as early as 1890. More than a century after these primitive efforts, profound advancements in imaging, instrumentation, and operative techniques have greatly improved the modern surgeon's ability to treat such lesions successfully, often with curative results. METHODS: We review the history of intramedullary spinal cord tumor surgery, as well as the evolution and advancement of technologies and surgical techniques that have defined the procedure over the past 100 years. RESULTS: Surgery to remove intramedullary spinal cord tumors has evolved to include sophisticated imaging equipment to pinpoint tumor location, laser scalpel systems to provide precise incisions with minimal damage to surrounding tissue, and physiological monitoring to detect and prevent intraoperative motor deficits. CONCLUSION: Modern surgical devices and techniques have developed dramatically with the availability of new technologies. As a result, continual advancements have been achieved in intramedullary spinal cord tumor surgery, thus increasing the safety and effectiveness of tumor resection, and progressively improving the overall outcomes in patients undergoing such procedures.