Alterações do esqueleto axial e complicações neurológicas na acondroplasia

Abstract

Background: Achondroplasia is the most common non-lethal skeletal dysplasia and there is disproportion between bone and neural structures development. The foramen magnum and spinal canal present underdevelopment compared with the central nervous system. It is associated with neurological complications. Purposes: to study the axial skeleton and the neurological complications of achondroplasia in patients treated at a rehabilitation hospital between May of 1998 and June of 2013. Method: The project was approved by the Ethics and Research Committee at UFMG and SARAH Network (Plataforma Brasil recorded in CAAE 03970712.5.3001.0022). This is a cross-sectional and a retrospective clinical and radiological observational study. The review of 41 medical records of patients with a definitive or differential diagnosis of achondroplasia was performed and they were called for interview. The patients or their legal guardians agreed to participate, read and signed the consent form. The patients were divided into two groups: one with children younger than eight years old and other with older individuals. Only patients with confirmed molecular genetic testing participated in the study. The same medical geneticist examined all patients. The development, weight, height, head circumference, pedigree, obstetric history and neurological symptoms were evaluated. Brain CT scans and CVJ dynamic flexion-extension CT studies were performed. A helical scanner was used for a volumetric acquisition by axial slices with 2.5 mm thickness and interval, reconstructed with 0.625 mm for multiplanar reformation. It was used techniques with lower kilovoltage and exposure time to reduce radiation exposure (ALARA safety principle). For the craniometry, the arithmetic mean of three measurements were made by two radiologists were used. The following parameters were evaluated: Welcher angle, dens tip position above McGregor line, Redlund-Johnell method, atlantodens interval, width of the spinal canal at C2 segment, basion-dens interval, lengths of posterior axial line, condylar displacement and Powers ratio. To measure the ventricles were used: Evans ratio, cerebroventricular index of the anterior horns and maximum width of the third ventricle. When there were signs and/or symptoms of neurological damage, roentgen, computed tomography and magnetic resonance were performed. To assess the size of the ventricles and foramen magnum, 96 normal scans of skull were selected as control group among CT scans performed in the same hospital, in the proportion of four to one, according to age and sex criteria. Statistical analysis used the t-test (to compare means), Kruskal-Wallis test (for differences between means) and Fisher test (to compare groups). A p-value<0.05 threshold was considered for statistical significance. Results: twenty-four patients with molecular confirmation of achondroplasia were included in the study. Eleven of them were younger than eight years old, 13 were females, all cases were sporadic and the paternal age was high in 53%. Prenatal ultrasound in 71% detected short limbs in 53%. The following CVJ findings were found: narrowing of the diameter of the foramen magnum transverse (100%) and anteroposterior (96%), spinal stenosis at C2 (92%), clivus hypoplasia (88%), atlanto-occipital instability (25%), atlantoaxial instability (13 %), basilar invagination (13%) was more common in older individuals, platybasia (8%). The following brain findings were found: ventriculomegaly (30%), lack of hemispheric sulci (13%), subarachnoid space obliteration (9%). Other findings in the exams were sinusitis (79%) and post-tympanic secretion (25%). There was no upper cervical compressive myelopathy. Affected patients had neurological symptoms in 54%: in 33% with upper cervical spinal stenosis, 29% with lower thoracolumbar spinal stenosis and all from the older group, and in 8% there is spinal stenosis in both levels, all adults. There were signs of lower thoracolumbar compressive myeloradiculopathy in 17%. Conclusion: the study of the axial skeleton and neurological complications in patients with achondroplasia contributed for professionals involved in the monitoring, prevention and treatment of the affected individuals.