Updates on Intraoperative Neurophysiology During Surgery for Spinal Dysraphism.

Spinal dysraphism is a group of disorders resulting from an embryologic failure of spinal cord development which can lead to a radicular-medullary mechanical stretch that generates vascular compromise and hypoxic-ischemic damage to the nervous structures of the conus-cauda region.Thus, the clinical relevance of the different types of spinal dysraphism is related to the possible neurologic deficits resulting from spinal cord tethering. The clinical presentation is heterogenous: from asymptomatic to very compromised patients. The indications and the time of a detethering surgery are still subject of debate, although there is an agreement on the high standards of treatment that have to be offered by the surgery. Intraoperative neurophysiology (ION) contributes to the safety of tethered cord surgery in reducing the risks of iatrogenic neurological damages.

Very early and early neurophysiological abnormalities in Guillain-Barré syndrome: A 4-year retrospective study.

BACKGROUND AND PURPOSE: In its initial stages, Guillain-Barré syndrome (GBS) is difficult to identify, because diagnostic criteria may not always be fulfilled. With this retrospective study, we wanted to identify the most common electrophysiological abnormalities seen on neurophysiological examination of GBS patients and its variants in the early phases. METHODS: We reviewed the clinical records of patients admitted to our Neurology Unit with a confirmed diagnosis of GBS. The study sample was divided in two subgroups according to whether the neurophysiological examination was performed: within 7 days (very early group) or within 7-15 days (early group). H reflex, F waves, and motor and sensory conduction parameters were judged abnormal if they were outside the normal range for at least two nerves. We evaluated neurophysiological findings in Miller-Fisher syndrome (MFS) separately. RESULTS: The study sample comprised 36 patients. In GBS, the most frequent abnormal neurophysiological parameter was the bilateral absence of the H reflex, followed by F wave abnormalities. Motor conduction parameters were altered in less than 50% of patients, and even less common were sensory nerve action potential reduction and the "sural-sparing" pattern. In MFS, H reflex was absent bilaterally in 100% of patients, followed by a predominant peripheral sensory involvement, whereas motor conduction parameters were frequently normal. CONCLUSIONS: Bilateral absence of the H reflex is the most sensitive parameter in early diagnosis of GBS and its variants.

Utility of Preoperative Electrodiagnosis Together with Peripheral Nerve High-Resolution Ultrasound: A Complex Case Report of Neurofibromatosis Type I.

Our case report underscores the importance of electroneuromyography (ENMG) combined with peripheral nerve high-resolution ultrasound (HRUS) in the evaluation of neurofibromatosis type 1 (NF1). A 49-year-old woman affected by NF1 came to our attention because of new-onset left arm weakness and atrophy. Debulking of a cervicothoracic C7-T1 neurofibroma had been performed 8 years earlier. On current admission, magnetic resonance imaging disclosed increased lesion volume that was thought to cause the neurologic deficits by compressing the C8 root. Findings from intraoperative neurophysiologic monitoring during repeat debulking suggested that C8 root integrity had been compromised during the first operation and that the new-onset symptoms probably stemmed from peripheral nervous system damage distal to the cervical roots. Postoperative ENMG showed chronic denervation signs in the muscles innervated by C7-C8-T1 roots, moderate carpal tunnel syndrome (CTS), and ulnar nerve conduction block at the elbow. HRUS confirmed the CTS and revealed multiple neurofibromas involving the distal tract of the radial, ulnar, and median nerves. Surgical debulking was considered unnecessary in this case. ENMG combined with nerve and plexus HRUS evaluation may help identify the cause of neurologic deficits and choose the best surgical option in such complex clinical conditions as NF1.

Feasibility of cerebello-cortical stimulation for intraoperative neurophysiological monitoring of cerebellar mutism.

BACKGROUND: Cerebellar mutism can occur in a third of children undergoing cerebellar resections. Recent evidence proposes it may arise from uni- or bilateral damage of cerebellar efferents to the cortex along the cerebello-dento-thalamo-cortical pathway. At present, no neurophysiological procedure is available to monitor this pathway intraoperatively. Here, we specifically aimed at filling this gap. METHODS: We assessed 10 patients undergoing posterior fossa surgery using a conditioning-test stimulus paradigm. Electrical conditioning stimuli (cStim) were delivered to the exposed cerebellar cortex at interstimulus intervals (ISIs) of 8-24 ms prior to transcranial electric stimulation of the motor cortex, which served as test stimulus (tStim). The variation of motor-evoked potentials (MEP) to cStim + tStim compared with tStim alone was taken as a measure of cerebello-cortical connectivity. RESULTS: cStim alone did not produce any MEP. cStim preceding tStim produced a significant inhibition at 8 ms (p < 0.0001) compared with other ISIs when applied to the lobules IV-V-VI in the anterior cerebellum and the lobule VIIB in the posterior cerebellum. Mixed effects of decrease and increase in MEP amplitude were observed in these areas for longer ISIs. CONCLUSIONS: The inhibition exerted by cStim at 8 ms on the motor cortex excitability is likely to be the product of activity along the cerebello-dento-thalamo-cortical pathway. We show that monitoring efferent cerebellar pathways to the motor cortex is feasible in intraoperative settings. This study has promising implications for pediatric posterior fossa surgery with the aim to preserve the cerebello-cortical pathways and thus prevent cerebellar mutism.

Long-term motor deficit in brain tumour surgery with preserved intra-operative motor-evoked potentials.

Muscle motor-evoked potentials are commonly monitored during brain tumour surgery in motor areas, as these are assumed to reflect the integrity of descending motor pathways, including the corticospinal tract. However, while the loss of muscle motor-evoked potentials at the end of surgery is associated with long-term motor deficits (muscle motor-evoked potential-related deficits), there is increasing evidence that motor deficit can occur despite no change in muscle motor-evoked potentials (muscle motor-evoked potential-unrelated deficits), particularly after surgery of non-primary regions involved in motor control. In this study, we aimed to investigate the incidence of muscle motor-evoked potential-unrelated deficits and to identify the associated brain regions. We retrospectively reviewed 125 consecutive patients who underwent surgery for peri-Rolandic lesions using intra-operative neurophysiological monitoring. Intraoperative changes in muscle motor-evoked potentials were correlated with motor outcome, assessed by the Medical Research Council scale. We performed voxel-lesion-symptom mapping to identify which resected regions were associated with short- and long-term muscle motor-evoked potential-associated motor deficits. Muscle motor-evoked potentials reductions significantly predicted long-term motor deficits. However, in more than half of the patients who experienced long-term deficits (12/22 patients), no muscle motor-evoked potential reduction was reported during surgery. Lesion analysis showed that muscle motor-evoked potential-related long-term motor deficits were associated with direct or ischaemic damage to the corticospinal tract, whereas muscle motor-evoked potential-unrelated deficits occurred when supplementary motor areas were resected in conjunction with dorsal premotor regions and the anterior cingulate. Our results indicate that long-term motor deficits unrelated to the corticospinal tract can occur more often than currently reported. As these deficits cannot be predicted by muscle motor-evoked potentials, a combination of awake and/or novel asleep techniques other than muscle motor-evoked potentials monitoring should be implemented.

Genetic profile of patients with early onset inflammatory bowel disease.

Inflammatory Bowel disease (IBD) is a widespread pathological condition with clinical heterogeneity and with different levels of severity. Although IBD usually occurs in young adults, onset in childhood and infancy are described in patients within the 10th and second year of age. By genome-wide association studies and meta-analysis, several genetic loci have been identified associated with an increased risk of developing IBD in Western populations with variants that may alter the normal mucosal immunity in the gastrointestinal tract. The clinical complexity and the heterogeneity of the IBD phenotype probably reflect the presence of genetic heterogeneity where different genes or combinations of them may be involved, together with environmental factors. We hypothesized that patients with early onset IBD could have either more severe genetic variants in genes associated with IBD or multiple variants in different genes. Under the multifactorial diseases is crucial to consider the small contribution of a single variant in all not only to other small variations in the same gene but also in different genes belonging to the same pathway. We performed direct gene sequencing looking for 94 variations in NOD2, ATG16L1, IL23R, IL10R, IL10 and XIAP genes previously shown as correlated with IBD both in multifactorial and in Mendelian models. All variants identified are known in literature as being associated with IBD except for three variants in the genes NOD2, IL10 and IL10RB that even though present in online databases have never been involved in association studies on IBD patients. Moreover, we coupled genetic variants identification with an accurate "in silico" analysis to verify their predictive impact on the protein structure and function. The in-silico prediction of these variants results as benign therefore even if they exhibit a very low frequency in control population being benign, they cannot be considered pathogenic as monogenic disease but fall within the multifactorial range. The variants identified in our study partially reflect the association data described in the literature but there are no significant differences with the onset of disease (VEO vs EO-IBD).

Intra-operative neurophysiological mapping and monitoring during brain tumour surgery in children: an update.

INTRODUCTION: Over the past decade, the reluctance to operate in eloquent brain areas has been reconsidered in the light of the advent of new peri-operative functional neuroimaging techniques and new evidence from neuro-oncology. To maximise tumour resection while minimising morbidity should be the goal of brain surgery in children as much as it is in adults, and preservation of brain functions is critical in the light of the increased survival and the expectations in terms of quality of life. DISCUSSION: Intra-operative neurophysiology is the gold standard to localise and preserve brain functions during surgery and is increasingly used in paediatric neurosurgery. Yet, the developing nervous system has peculiar characteristics in terms of anatomical and physiological maturation, and some technical aspects need to be tailored for its use in children, especially in infants. This paper will review the most recent advances in the field of intra-operative neurophysiology (ION) techniques during brain surgery, focussing on those aspects that are relevant to the paediatric neurosurgery practice.

The importance of polysomnography in the evaluation of prolonged disorders of consciousness: sleep recordings more adequately correlate than stimulus-related evoked potentials with patients' clinical status.

OBJECTIVES: The aim of our study was to evaluate the importance of sleep recordings and stimulus-related evoked potentials (EPs) in patients with prolonged disorders of consciousness (DOCs) by correlating neurophysiologic variables with clinical evaluation obtained using specific standardized scales. METHODS: There were 27 vegetative state (VS) and 5 minimally conscious state (MCS) patients who were evaluated from a clinical and neurophysiologic perspective. Clinical evaluation included the Coma Recovery Scale-Revised (CRS-R), Disability Rating Scale (DRS), and Glasgow Coma Scale (GCS). Neurophysiologic evaluation included 24-h polysomnography (PSG), somatosensory EPs (SEPs), brainstem auditory EPs (BAEPs), and visual EPs (VEPs). RESULTS: Patients with preservation of each single sleep element (sleep-wake cycle, sleep spindles, K-complexes, and rapid eye movement [REM] sleep) always showed better clinical scores compared to those who did not have preservation. Statistical significance was only achieved for REM sleep. In 7 patients PSG showed the presence of all considered sleep elements, and they had a CRS-R score of 8.29±1.38. In contrast, 25 patients who lacked one or more of the sleep elements had a CRS-R score of 4.84±1.46 (P<.05). Our multivariate analysis clarified that concurrent presence of sleep spindles and REM sleep were associated with a much higher CRS-R score (positive interaction, P<.0001). On the other hand, no significant associations were found between EPs and CRS-R scores. CONCLUSIONS: PSG recordings have proved to be a reliable tool in the neurophysiologic assessment of patients with prolonged DOCs, correlating more adequately than EPs with the clinical evaluation and the level of consciousness. The main contribution to higher clinical scores was determined by the concomitant presence of REM sleep and sleep spindles. PSG recordings may be considered inexpensive, noninvasive, and easy-to-perform examinations to provide supplementary information in patients with prolonged DOCs.