Assessment of brainstem function in Chiari II malformation utilizing brainstem auditory evoked potentials (BAEP), blink reflex and masseter reflex

Audiological evaluation in children affected by myelomeningocele

PURPOSE

The aim of the present study is to evaluate the auditory system in children affected by myelomeningocele and comparing the results with clinical neurological conditions.

MATERIALS AND METHODS

Forty-three children, aged between 7 and 26 years, affected by myelomeningocele were investigated by means of subjective tonal audiometry and objective impedance audiometry (tympanometry and acoustic stapedial reflex).

RESULTS

Audiological evaluation showed an alteration in 32 patients (74%%). Nine patients presented a mild hearing loss: bilateral in six cases (three sensorineural, one mixed, and two conductive) and unilateral in three cases (two mixed and one conductive). One patient had moderate unilateral conductive deafness and, finally another one severe unilateral sensorineural. Almost all patients with deafness were affected by myelomeningocele and Chiari II. Stapedial-cochlear reflex investigation showed an alteration in 30 patients (70%): 9 of these also showed deafness while the remaining 21 was normal hearing. In these 30 patients, we demonstrated the presence of myelomeningocele, hydrocephalus, and Chiari II malformation in 21 subjects (70%).

CONCLUSION

Otoneurological evaluation is important in myelomeningocele not only at the birth but also in the follow-up. It could have an important prognostic role for neurological impairment.

Prognostic value of newborn hearing screening in patients with myelomeningocele

OBJECT

Brainstem dysfunction occurs in a minority of patients with myelomeningocele (MMC), most of whom have Chiari Type II malformation. Some surgeons advocate early identification of these patients for craniocervical decompression to avoid significant mortality. The auditory brainstem response has been found to be abnormal in most children with MMC. The present study examines whether failure of routine newborn hearing screening (NHS) predicts brainstem dysfunction in MMC patients.

METHODS

The charts of 40 newborns with MMC and 50 newborns without MMC who stayed in the neonatal intensive care unit were reviewed. Results of NHS, brainstem symptoms, birth demographics, and surgical history were retrospectively examined. Differences in the presence and onset of brainstem symptoms by NHS result were assessed.

RESULTS

Failure of NHS was more common among newborns with MMC who developed brainstem symptoms (31%, 4 of 13 patients) than among newborns without MMC (0%, 0 of 50 patients; p = 0.001). Among the 40 newborns with MMC, brainstem symptoms were more common in those who failed NHS (80%, 4 of 5 patients) than in those who passed (26%, 9 of 35 patients; p = 0.031). Respiratory symptom onset occurred later in patients who failed NHS (median 16 months) than among those who passed (median 0 months; p = 0.022). The positive and negative predictive values of NHS for brainstem dysfunction in MMC were 0.80 and 0.74, respectively.

CONCLUSIONS

Results of NHS may help predict future brainstem dysfunction in patients with MMC and may be useful to incorporate into prognostic assessment and surgical decision making.

The neurophysiological balance in Chiari type 1 malformation (CM1), tethered cord and related syndromes

The Chiari malformation (CM) is a syndrome embodied in heterogeneous groups of malformations, spanning from the more benign and known, the CM1, to more complex syndromes such as the rare association with the tethered cord, as spinal lipomas, and the CM2, associated to open spina bifida. The clinical picture may be well expressed and detected at birth or even during intrauterine life, as for CM2, but in the other cases they may run a rather subtle clinical course. The diagnosis of these syndromes is driven by clinical examination and MRI, and it usually requires a multidisciplinary approach in order to plan the therapeutic strategies, such as surgery. Among the diagnostic investigations, the imaging techniques represent the most useful, for their capabilities to detect subclinical lesions, such as syringomyielia and lipoma; the urological investigation is useful to evaluate the urogenital dysfunctions. The neurophysiological investigations represent a non invasive diagnostic procedure to investigate the peripheral nerve, the spinal cord, the brainstem functionalities and more higher brain functions; the nerve conduction studies and the cranial reflexes, the brainstem (BAEP) and the somatosensory (SEPs) evoked potentials (EPs), alone or in combination, can be used for the diagnosis, follow-up and intraoperative monitoring. The most useful diagnostic tools in CM1 are likely represented by the brainstem auditory evoked potentials (BAEPs) and the blink-reflex (BR), while the usefulness of SEPs is still doubtful and debated; in CM2 and tethered cord the neurophysiological techniques can be combined in different ways in order to make a functional balance and to answer specific questions. BAEPs and BR can be useful to investigate the brain stem functionality and SEP to evaluate whether the ascending sensory pathway to the cortex can be hampered at some level; the visual EPs are particularly useful to evaluate the integrity of posterior visual pathway and visual cortex in the case of associated hydrocephalus. In the tethered cord, both nerve conduction study and somatosensory evoked potentials (SEPs) are useful to evaluate motor and sensory dysfunction of the lombosacral roots and nerves and spinal cord for their capability to detect subclinical impairment of conduction along the sensory and motor pathway. Finally, last but not the least, the neurophysiological techniques are remarkably useful during surgery; the intraoperative monitoring (IOM) by means of electromyography and direct nerve stimulation and recordings are able to detect early nerve damage, minimize nerve lesions and optimise the surgical techniques. In the operated children with incomplete removal of lipoma and/or persistent tethering, the recordings of SEP and BAEP are useful to demonstrate a conduction deterioration along the ascending sensory pathway due to increasing tethering of the spinal cord due to somatic growth.

[Chiari II malformation. Supportive and predictive value of brainstem reflex and EAEP recordings]

BACKGROUND

In about 20% of patients with Chiari II malformation brainstem signs and symptoms occur. Ventilatory dysfunction is the main cause of death in these patients. The indication for craniocervical decompression is based on clinical examination because supporting electrophysiological or radiological methods were lacking.

METHODS

In a prospective study the clinical courses of 106 patients were documented during a 3-year period. In addition brainstem diagnostic procedures using the masseter reflex (MR), blink reflex (BR) and early auditory evoked potentials (EAEP) were done. Based on the model of binary logistic regression the odds ratio (OR) of progression over time was calculated.

RESULTS

The combination of MR and late BR components showed the highest correlation with clinical findings (OR: 23). The highest predictive value regarding clinical progression over a 3-year period was shown by the combined evaluation of MR, late BR components and EAEP interpeak latency I-V (OR: 17.6). Signs and symptoms had no predictive value.

CONCLUSIONS

Combined brainstem reflex recordings (MR and late BR components) support the clinical examination. To evaluate the long-term prognosis brainstem reflexes and EAEP recordings should be used.

Masseter reflex in childhood and adolescence

We report normative data of masseter reflex from a group of 54 children 2-16 years of age. For statistical analysis, the patients were divided into five age groups: 2-4, 5-7, 8-10, 11-13, and 14-16 years of age. A tap to the chin, using a hammer with a trigger device, elicited the masseter reflex. The response was recorded by surface electrodes. The onset latency and peak-to-peak amplitude of the averaged curve of eight reflex responses were measured. The reflex response could be recorded in all children and adolescents of all groups. The mean latency shortened from age 2 to 7 and was stable at the age of 8 years. As a sign of maturation, the increase of amplitude corresponded to the shortening of latency and was also stable at the age of 8 years. Abnormal side differences in latency of 0.9 ms (age group 2-4 years), 1.1 ms (age group 5-7 years), and 0.8 ms (age group 8-16 years) were evaluated. An amplitude ratio (lower amplitude divided by higher one) above 0.33 was calculated as normal.

Evaluation and management of the Chiari malformation type 1 for the primary care pediatrician

Diagnosis and treatment of CMI is undergoing reexamination that includes redefinition of the anatomic Chiari malformation and refinement and redefinition of the clinical syndrome. Children with SMI present with head pain of some kind, a neurologic deficit, or with signs of spinal cord dysfunction from syrinx. Some will present with no clinical syndrome at all. Presence of anatomic Chiari malformation or compelling clinical Chiari syndrome should lead to evaluation by a neurologist or neurosurgeon experienced with the syndromes and their treatment. Treatment options are varied but usually result in resolution of symptoms. When symptoms persist after surgery, management is complex and not uniformly successful, even in the most experienced hands.

Somatosensory evoked potentials in Arnold-Chiari malformation

Nearly all patients with repaired myelomeningoceles have an Arnold-Chiari (AC) malformation and about 20% of these patients develop clinical signs of brainstem dysfunction. The management of symptomatic AC malformation is still controversial and techniques are needed to provide an objective assessment of brainstem function. We recorded somatosensory evoked potentials (SEPs) in 52 patients aged between 8 months and 20 years (median 7.3 years) with AC malformation, to determine whether the SEPs discriminate patients with symptomatic AC malformation from those without symptoms. The subcortical far-field components P13, P14 and N18, which are generated within the brainstem, were recorded with non-cephalic reference electrodes and the cortical N20 with a frontal reference. Fourteen patients (27%) had signs and symptoms of brainstem dysfunction, which were related to the AC malformation. Abnormal SEPs were mainly recorded in symptomatic patients (sensitivity 0.7, specificity 0.9). The SEPs were particularly useful in patients from 4 years of age (sensitivity 0.9, specificity 0.9), but not in the younger age group. Abnormal somatosensory conduction reflects dysfunction of the brainstem or the upper cervical cord and may be clinically useful to assess patients with late onset symptomatic AC malformation.

Blink reflex alterations in recently diagnosed diabetic patients

OBJECTIVE

The aim of the present study was to determine the frequency of blink reflex alterations and to examine the influence of hyperglycemia in inducing the alterations in recently diagnosed Type 2 diabetes mellitus patients.

METHODS

A cross-sectional study was carried out on patients having asymptomatic diabetes with a period of evolution under 10 years. In all 47 patients (26 women and 21 men), serum glycemia levels were determined and the latency onset of the blink reflex components were measured.

RESULTS

The average patient age was 44.5+/-11.0 (mean+/-SD) years with a diabetes evolution period of 4.3+/-2.9 (mean+/-SD) years. After a fasting serum glucose test, the diabetic patients were catalogued as normoglycemic (< or =126 mg/dl) or as hyperglycemic (> 26 mg/dl) and subjected to a blink reflex test. The results obtained from the diabetic patients were compared with those from a non-diabetic control group. 14.8-31.9% of the diabetic patients showed alterations in blink reflex component latencies. The differences compared with the control group were significant (p<0.05).

CONCLUSIONS

Diabetes, as is well-known, can affect the central and peripheral nervous system and there does not appear to be a link between glycemic levels and blink reflex components. However, blink reflex alterations were present even in diabetic patients with a relatively short period of disease evolution.

Primary myelomeningocele closure and consequences

PURPOSE OF REVIEW

Myelomeningocele, the most frequently occurring open neural tube defect, requires lifelong care of the patient by medical professionals and by relatives. A basic understanding of the neurosurgical measures that have to be taken in the newborn, the infant, the child and the adult is important also for physicians of other disciplines involved in the treatment of patients with myelomeningocele.

RECENT FINDINGS

The most recent topic broadly discussed in this context is the role of foetal neurosurgery for closure of the neural tube defect. There is ongoing debate as to whether the beneficial postnatal effects of a prenatal operation in the unborn foetus outweighs the possible complications for the mother as well as the child.

SUMMARY

As some of the problems associated with myelomeningocele occur only later in life, it will still take many years until the beneficial, as well as the adverse, effects of prenatal neurosurgical procedures can be evaluated.