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.