Degenerative cervical myelopathy: Neuroradiological, neurophysiological and clinical correlations in 27 consecutive cases.

•New insight into prognostic factors for recovery of clinical function following posterior decompression for degenerative cervical myelopathy.•An increase of IOM amplitude of at least 50% coupled with preoperative T2-only and diffuse T2 signal changes on MRI is a positive prognostic factors for clinical improvement 6 months after surgery.•Clinical improvement at 6 months follow-up can be expected in patients with T1 hypo intensity if a diffuse border of the lesion on T2 images is present.

Intraoperative neurophysiological monitoring for the resection of brain tumors in pediatric patients.

Intraoperative neurophysiology (ION) is the gold standard to map and monitor brain functions during supratentorial surgery in critical areas. This is of great value for the surgery of brain gliomas in adults, but the same ION techniques can be used in the pediatric population with respect to both epilepsy and brain tumor surgery. While the principles of most ION techniques are the same for adults and children, the developing nervous system has peculiar characteristics in terms of anatomical and physiological maturation of afferent and efferent pathways within the brain and the spinal cord. Accordingly, some adjustments, particularly with regards to stimulation parameters, are needed in younger children. This paper will review current ION techniques to assist during the resection of brain tumors in children, focusing on the aspects peculiar to mapping and monitoring of sensori-motor functions in the pediatric population. On the other hand, awake surgery, of common use in adult patients when aiming to identify cortical and subcortical cognitive functions, is of very limited use in children and will not be discussed here.

Trigeminal laser-evoked potentials: a neurophysiological tool to detect post-surgical outcome in trigeminovascular contact neuralgia.

BACKGROUND: The aim of this study was to explore the nociceptive system of patients affected by trigeminal neuralgia (TN) secondary to documented vascular contact who underwent microvascular decompression. For that purpose, we used the classical trigeminal reflexes and the trigeminal laser-evoked potentials (tLEPs) before and after surgery, in order to verify any possible change after decompression and determine if there was any correlation between the neurophysiological parameters and the clinical outcome. METHODS: Eleven patients affected by TN caused by trigeminovascular contact and 10 age-matched controls underwent conventional trigeminal reflexes (bilateral Blink Reflex/BR and Masseter Inhibitory Reflex stimulating infraorbital and mental nerves/MIR V2 and V3) and tLEPs. Patients repeated neurophysiological tests one week after surgery. RESULTS: Short-latency BR and MIR were normal in all patients before surgery and there was no statistical difference before and after surgery. Conversely, in patients before surgery, tLEPs' amplitudes were significantly lower in the affected than in the healthy side (p = 0.017 for V2 and 0.037 for V3 branches). After surgery, on the affected side, tLEP amplitude increased and the pre/post-operative difference was significant (p = 0.017 for V2 and 0.028 for V3 divisions). Nine patients referred satisfactory pain relief and the favourable clinical outcome correlated with the neurophysiological recovery. CONCLUSIONS: This study demonstrates that TN caused by trigeminovascular compression may be related to Aδ fibres impairment, and tLEPs are more sensitive than conventional trigeminal reflexes to reveal small fibre dysfunction and to monitor the post-surgical outcome in these patients.

Monitoring of motor pathways during brain stem surgery: what we have achieved and what we still miss?

Intraoperative neurophysiological monitoring (IOM) has established itself as one of the paths by which modern neurosurgery can improve surgical results while minimizing morbidity. IOM consists of both monitoring (continuous "on-line" assessment of the functional integrity of neural pathways) and mapping (functional identification and preservation of anatomically ambiguous nervous tissue) techniques. In posterior-fossa and brainstem surgery, mapping techniques can be used to identify - and therefore preserve - cranial nerves, their motor nuclei and corticospinal or corticobulbar pathways. Similarly, free-running electromyography (EMG) and muscle motor-evoked potential (mMEP) monitoring can continuously assess the functional integrity of these pathways during surgery. Mapping of the corticospinal tract, at the level of the cerebral peduncle as well as mapping of the VII, IX-X and XII cranial nerve motor nuclei on the floor of the fourth ventricle, is of great value to identify "safe entry-zones" into the brainstem. Mapping techniques allow recognizing anatomical landmarks such as the facial colliculus, the hypoglosseal and glossopharyngeal triangles on the floor of the fourth ventricle, even when normal anatomy is distorted by a tumor. On the basis of neurophysiological mapping, specific patterns of motor cranial nuclei displacement can be recognized. However, brainstem mapping cannot detect injury to the supranuclear tracts originating in the motor cortex and ending on the cranial nerve motor nuclei. Therefore, monitoring techniques should be used. Standard techniques for continuously assessing the functional integrity of motor cranial nerves traditionally rely on the evaluation of spontaneous free-running EMG in muscles innervated by motor cranial nerves. Although several criteria have been proposed to identify those EMG activity patterns that are suspicious for nerve injury, the terminology remains somewhat confusing and convincing data regarding a clinical correlation between EMG activity and clinical outcome are still lacking. Transcranial mMEPs are also currently used during posterior-fossa surgery and principles of MEP monitoring to assess the functional integrity of motor pathways are similar to those used in brain and spinal-cord surgery. Recently, current concepts in muscle MEP monitoring have been extended to the monitoring of motor cranial nerves. So-called "corticobulbar mMEPs" can be used to monitor the functional integrity of corticobulbar tracts from the cortex through the cranial motor nuclei and to the muscle innervated by cranial nerves. Methodology for this purpose has appeared in the literature only recently and mostly with regards to the VII cranial nerve monitoring. Nevertheless, this technique has not yet been standardized and some limitations still exist. In particular, with regards to the preservation of the swallowing and coughing reflexes, available intraoperative techniques are insufficient to provide reliable prognostic data since only the efferent arc of the reflex can be tested.