Subcortical somatosensory evoked potentials after posterior tibial nerve stimulation in children

Evaluation of Neurological Examination, SEP Results, MRI Results, and Lesion Levels in Patients Who Had Been Operated for Myelomeningocele

Objective:

Myelomeningocele is the most severe and the most frequent form of spina bifida. Most of the myelomeningocele patients undergo operations in new-born age. In terms of life quality and rehabilitation, follow-up’s of these patients in the growth and development period after the operation is critical. In our study, our aim is to emphasize the correlation of SEP results with MRI results and clinical features of the myelomeningocele patients.

Materials and Methods:

In our study, we included 36 patients who had undergone myelomeningocele operation and have been followed-up in Istanbul Bilim University Florence Nightingale Hospital, Spina Bifida Research and Treatment Centre. Posterior tibial nerve SEP was performed on each patient and neurological examinations were done in the same session. Results were compared with clinical functional lesion levels, levels of fusion defect and ambulation levels. In order to evaluate SEP results, we used age-related reference values from Boor et al.’s study in 2008. Patients were grouped as normal, unilaterally prolonged, bilaterally prolonged, unilaterally lost, and bilaterally lost.

Results:

The correlations of posterior tibial nerve SEP results were significant with ambulation levels (r = 0.428, P < 0.01), clinical functional lesion levels (r = 0.477, P < 0.01) and fusion defect levels (r = −0.528 P < 0.05). The lumbar SEP results were only significantly correlated with functional lesion levels (r = 0.443 P < 0.05).

Conclusions:

Radiological studies are insufficient when evaluating the functionality of the central nervous system. To fully evaluate the functionality and watch the neurological development with accuracy, especially in operated patients, electrophysiological studies should be an indispensable part of myelomeningocele follow-ups.

Corticospinal tract damage in HHH syndrome: a metabolic cause of hereditary spastic paraplegia

BACKGROUND

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a rare disorder of urea cycle characterized by progressive pyramidal and cerebellar dysfunction, whose pathophysiology is not yet fully understood. Here we describe the spectrum of the long fibers involvement in HHH syndrome, attempting a correlation between clinical, electrophysiological and neuro-radiological data.

METHODS

Nine HHH patients were longitudinally evaluated by clinical examination, neurophysiological assessment including motor (MEPs), somato-sensory evoked potentials (PESS) and nerve conduction velocity (NCV), brain and spinal cord MRI RESULTS: All patients had pyramidal dysfunction and 3/9 an overt spastic paraplegia. Mild to moderate cerebellar signs were found in 7/9, intellectual disability in 8/9. At lower limbs, MEPs resulted abnormal in 7/8 patients and PESS in 2/8; peripheral sensory-motor neuropathy was found in 1/9. MRI documented atrophic changes in supra-tentorial brain regions in 6/9 patients, cerebellum in 6/9, spinal cord in 3/7.

CONCLUSIONS

A predominant corticospinal dysfunction is evident in HHH syndrome, along with milder cerebellar signs, intellectual disability of variable degree and rare peripheral neuropathy. Phenotypical similarities with other disorders affecting the urea cycle (argininemia and pyrroline-5-carboxylate synthetase deficiency) suggest possible common mechanisms contributing in the maintenance of the corticospinal tract integrity. HHH syndrome phenotype largely overlaps with complex Hereditary Spastic Paraplegias (HSPs), in the list of which it should be included, emphasizing the importance to screen all the unsolved cases of HSPs for metabolic biomarkers.

PIEZO2 deficiency is a recognizable arthrogryposis syndrome: A new case and literature review

PIEZO2 encodes a mechanically activated cation channel, which is abundantly expressed in dorsal root ganglion neuron and sensory endings of proprioceptors required for light touch sensation and proprioception in mice. Biallelic loss-of-function mutations in PIEZO2 (i.e., PIEZO2 deficiency) were recently found to cause an arthrogryposis syndrome. Sixteen patients from eight families have been reported to date. Herein we report a new case, including detailed clinical characteristics and courses as well as comprehensive neurological features. The patient was a 12-year-old girl presenting with congenital multiple contractures, progressive severe scoliosis, prenatal-onset growth impairment, motor developmental delay with hypotonia and myopathy-like muscle pathology, mild facial features, and normal intelligence. Her neurological features included areflexia, impaired proprioception, and decreased senses. Neurophysiological examination revealed decreased amplitude of sensory nerve action potentials, absent H reflex, and prolongation of central conduction times. Clinical exome sequencing revealed a novel homozygous frameshift mutation in PIEZO2 (NM_022068: c.4171_4174delGTCA: p.Val1391Lysfs*39) with no detectable mRNA expression of the gene. PIEZO2 deficiency represents a clinical entity involving characteristic neuromuscular abnormalities and physical features. Next generation sequencing-based comprehensive molecular screening and extensive neurophysiological examination could be valuable for diagnosis of the disorder.

Early impairment of somatosensory evoked potentials in very young children with achondroplasia with foramen magnum stenosis

AIM

To evaluate the contribution of somatosensory evoked potentials after median nerve (MN-SEPs) and posterior tibial nerve (PTN-SEPs) stimulation in functional assessment of cervical and lumbar spinal stenosis in children with achondroplasia.

METHOD

We reviewed MN-SEPs, PTN-SEPs, and spinal magnetic resonance imaging (MRI) examinations performed in 58 patients with achondroplasia (25 males, 33 females; age range 21d-16y 10mo; mean age 4y 3mo [SD 4y 1mo]). Patients were subdivided into four age categories: <2 years, between 2 to 4 years, between 4 to 8 years, and ≥8 years. The peak latency of P37 for PTN-SEPs, the peak latencies of N11, N13, P14, and N20, and the N13-N20 interpeak latency (IPL) for MN-SEPs were collected; the diagnostic accuracy measures of these parameters (analysis of receiver operating characteristic [ROC] curves) with respect to the presence of foramen magnum or lumbar spinal stenosis were analysed in each age category.

RESULTS

The ROC curve analysis showed that the most sensitive parameter in detecting the presence of foramen magnum stenosis was P37 latency in the first two age categories (<2y and ≥2-4y; sensitivity 0.63, specificity 1.00, and sensitivity 1.00, specificity 0.75 respectively). In the third age category (≥4-8y), the most sensitive parameter in detecting the presence of foramen magnum stenosis was IPLs N13-N20 (sensitivity 0.73, specificity 0.87), whereas in the last age category (≥8y), the most important parameter was N20 latency (sensitivity 0.75, specificity 0.77).

INTERPRETATION

In children with achondroplasia, the cortical component of PTN-SEPs is more sensitive than the cortical component and central conduction time of MN-SEPs in detection of cervical spinal cord compression at early ages.

Intraoperative monitoring in pediatric orthopedic spinal surgery: three hundred consecutive monitoring cases of which 10% of patients were younger than 4 years of age

STUDY DESIGN

Analysis of a prospective series of 300 consecutive cases undergoing intraoperative monitoring in pediatric orthopedic spinal surgery, of which 10% were children younger than 4 years.

OBJECTIVE

Determine feasibility and performance of intraoperative monitoring in children younger than 4 years. Analyze distinct physiopathologic mechanisms of relevant alerts.

SUMMARY OF BACKGROUND DATA

There are few studies in the literature concerning the intraoperative monitoring of children younger than 4 years. During childhood, the development of sensori-motor pathways is dominated by two coexisting phenomena, which have opposite effects: maturation decreasing latencies and height increasing them.

METHODS

We used intraoperative somatosensory-evoked potentials and neurogenic mixed evoked potentials with a flexible bipolar epidural electrode. Uniform total intravenous anesthesia was used.

RESULTS

Values of sensitivity and specificity of the monitoring showed slight differences between patients younger than 4 years versus older patients. There was no false-negative outcome. Various tendencies were highlighted. There were more true positive alerts for secondary etiologies than for idiopathic ones, for revision spinal surgeries than for index ones, and for boys than for girls. There were no more true positive alerts for children younger than 4 years than for older patients whereas the proportion of hemivertebrae was obviously greater for the younger group. Relevant monitoring alerts were more frequent in case of kyphoscoliosis. This is highlighted in case reports.

CONCLUSION

In some cases of kyphoscoliosis, during a posterior-based vertebral column resection, monitoring changes were corrected by positioning a rod that allowed correction of the position of the spine in the sagittal plane. Intraoperative spinal cord monitoring can be performed in children younger than 4 years and allows real-time assessment of spinal functional integrity.

Improving successful rate of transcranial electrical motor-evoked potentials monitoring during spinal surgery in young children

INTRODUCTION

This prospective study was to investigate the successful rate of intraoperative motor evoked potentials (MEP) monitoring for children (<12 years old) with congenital scoliosis.

MATERIALS AND METHODS

A consecutive series of 27 young children (7 girls and 20 boys; from 1 to 11 years old) between September 2007 and November 2009, were enrolled to this study. 12 patients received general anesthesia based on TIVA, induced with propofol 2-4 mg/kg and fentanyl 3-5 µg/kg followed by a continuous infusion of propofol (20-150 µg/kg/min, at mean of 71.7 µg/kg/min). The other 15 patients received combined inhalation and intravenous anesthesia, induced with sevoflurane and fentanyl 3-5 µg/kg and maintained by sevoflurane (0.5-1%). The maintenance of anaesthesia management was performed with stable physiological parameters during surgery.

RESULTS

Intraoperative MEP monitoring was successfully performed in all patients, while SEP was successfully performed in 26 of 27 patients. There was no significant difference of successful rates between SEP and MEP monitoring (P > 0.05). As well, no difference in MEP successful rates was observed in two groups with different anesthetic techniques. No wake-up test and no post-operative neurological deficits occurred in this series of patients.

CONCLUSION

Low dose anesthesia by either TIVA with propofol or sevoflurane-based mixture anesthesia protocol can help the intraoperative spinal cord monitoring to successfully elicit MEP and perform reliable monitoring for patients below 12 years of age.

Neurophysiological changes induced by the botulinum toxin type A injection in children with cerebral palsy

In the last few years botulinum toxin type A (BTX-A) has been widely used in the management of spasticity in children with cerebral palsy in order to reduce hypertonicity and improve functional outcomes enhancing motor skill development. The botulinum toxin injection seems to interact with intrafusal and extrafusal fibers producing a reduction of hypertone both through synaptic blockade and inhibition of stretch reflex loop and these changes may influence not only the spinal cord but also the central nervous system (CNS). The purpose of our study was to determine the neurophysiological changes induced by the BTX-A through an evaluation of cortical somatosensory Evoked Potential (SEP) and Soleus H wave, that is the index of excitability of stretch reflex loop. Eighteen children with Cerebral Palsy (CP), aged between 5 and 12, were recruited at Children's Hospital "Bambino Gesù" of Rome. All children were evaluated with appropriate clinical scales before and 1 month after the BTX-A injection. Neurophysiological measurements were performed before, and 1 month after botulinum toxin injection through lower limb SEPs, M-wave and Soleus H wave recording. After the injection the results showed a statistically significant improvement both of clinical scales and the neurophysiological variables. These findings suggest that spasticity itself can be considered as a factor affecting the cortical SEPs. And even though it seems that BTX-A does not have any direct central effect on sensory pathways we suppose an indirect mechanism on modulation of afferent fibers Ia due to the modification induced by BTX-A to central loop reflex.

Evoked potential studies can only be interpreted as a neurophysiologic measure if applied accurately

Evoked potentials are commonly used in neurology but standardized protocols have to be carried out during both application and evaluation. Otherwise adequacy and reliability might be questioned, which is unacceptable in evidence-based modern science. Both motor and somatosensory evoked potential studies can only be interpreted as a neurophysiologic measure in cord lesions if applied irreproachably.