Postual Control in Pediatric Chiari I Malformation

Chiari malformation is characterized by at least 5 mm descent of cerebellar tonsils below the foramen magnum, into the vertebral canal. Historical classification of this malformation consists in four different types, but it is the first one, due to a congenital small posterior fossa, which represent our focus of interest. Chiari malformation may leads to direct brainstem compression and to cerebrospinal fluid circulation trouble at this level, being cause of classical associated phenomena such as syringomyelia formation.

The clinical manifestation may be resumed as follow:

• Exertional headaches or neck pain.
• Brainstem compression signs and symptoms (central apneas syndrome, tetraparesis, paresthesia, cranial nerves disfunction...).
• Syringomyelia signes and symptoms (neuropathic pain, suspended hypo-anesthesia).

The only treatment for Chiari I malformation is the surgical one. It consists in an osteo-dural decompression of the posterior fossa. Surgical decision is formal when at least one of the following criteria is satisfied:

• presence of syringomyelia;
• coexistence of central apneas syndrome;
• presence of the classical symptomatology. Nevertheless, the spectrum of symptoms which might be reported by the patient, and which has even been described in the non neurosurgical literature, is largely wider than the previously thought and assumed by the neurosurgeons. There are so several "atypical symptoms" in which neurosurgeons doesn't believed, and that don't constitute an indicator for surgical intervention. Among these "atypical symptoms" one cas find those ones who bring back to ear, nose and throat domain, such as nystagmus, dizziness, tinnitus, hear loss, and gait instability.

We decided to focalise about one of these symptoms, the gait instability, trying to find the link between Chiari malformation and postural control. In the literature, there are only one study concerning this aspect, conducted on an adult population with the help of a static posturography.

Our study will focus on pediatric patients, who will be evaluated by a dynamic posturography, the Equitest platform (NeuroCom, Clackamas, OR). This platform is able to quantify the contribution of each of the three sensory informations (visual, vestibular and somatosensory) necessary to maintain equilibrium, realising a specific test (Sensory Organisation Test).

The Equitest can elaborate a Composite Equilibrium Score (CES), that will be our PRIMARY JUDGMENT CRITERIA.

Only patients for which ENT evaluation is indicated for medical reasons (for example, children presented frequent falls, dizziness, nystagmus, motion sickness...) will be evaluated.

This evaluation won't change habitual neurosurgical care for the patients presenting Chiari I malformation, so two groups of patients will be identified: children who will be operated on and children who won't. CES of the two groups will be calculated and compared.

Furthermore, we will compared CES results of the operated patients group before and after surgery, to evaluate the impact of surgery on postural control.

In parallel, we will evaluate others SECONDARY CRITERIA in operated patient, before and after surgery, such as :

• signe and symptomss modification;
• decompression result on MRI images;
• syringomyelia modification, if present before;
• central apnea syndrome modification, if present before;
• scoliosis modification, if present before;
• behavioral modification. Anamnestic and clinical data will be part of the habitual computerized medical folder, as well as polysomnographic, posturographic and imaging ones.

Clinical elements of recruited patients will be collected by principal investigator in an anonymous database, secured by a password.

Concerning primary criteria, collected qualitative data will be analysed by Chi-2 or Fischer test, while quantitative ones will be analysed by Student's test or Mann-Whitney one.

Concerning secondary criteria, collected qualitative data will be analysed by Mc Nemar test or symmetry test, while quantitative ones will be analysed by Student's test Wilcoxon one.