Magnetic resonance imaging study determining cord level and occupancy at thoracolumbar junction in achondroplasia – A prospective study

BACKGROUND: Thoracolumbar (TL) stenosis in achondroplasia is frequently reported, and becomes symptomatic in adulthood. Hence we conducted a prospective study to determine cord level and occupancy at TL junction in symptomatic or asymptomatic achondroplasis patients in comparision to normal population by magnetic resonance imaging (MRI). MATERIALS AND METHODS: Cord level with its occupancy rate and TL kyphosis were measured on MRI and standing radiogram, respectively. We prospectively studied MRI of TL spine in 19 patients (7 males and 12 females) with achondroplasia. All the subjects were randomly selected from our outpatient clinic and divided into two groups: symptomatic and asymptomatic group. Symptomatic group had at least two of the following symptoms: back pain with spasticity and walking difficulty, radicular pain in upper thigh or girdle pain, tingling and numbness in the lower limbs, visible deformity at TL spine and brisk reflexes in lower extremities. Asymptomatic group was selected from those patients who visited in outpatient clinic for consultation of limb lengthening. The third group was taken as control that comprised 11 nonachondroplasia otherwise normal patients (8 males and 3 females) who presented to our outpatient clinic for back pain. RESULTS: Results showed spinal cord level was higher in achondroplasia than nonachondroplasia (P=0.003); however, no difference in cord level between symptomatic and asymptomatic group (P=0.568). Comparing cord occupancy, no difference found among all three groups (P=0.20). Kyphosis was increasing from nonachondroplasia, asymptomatic and symptomatic patient groups (P<0.001). Average age was 22.4±14.2, 11.9±6.5, and 36.2±13.2 years in symptomatic, asymptomatic, and nonachondroplasia groups, respectively (P<0.001). CONCLUSION: Our results indicated high level of spinal cord in achondroplasia patients compared to nonachondroplasia individuals. High prevalence of neurological symptoms at TL level in such patients can be associated with high cord level and developing progressive kyphosis at TL level along with degenerative process.