Ossification of the posterior longitudinal ligament of the cervical spine.

Although ossification of the posterior longitudinal ligament (OPLL) of the cervical spine is an uncommon condition, its strong prevalence among the Japanese and non-Japanese Asians is well known. Genetic predisposition coupled with ageing and an imbalance in bone-seeking hormones are some actiological factors postulated in recent years. Imaging is directed at showing the calcified mass, cord compression and any attendant damage, as the latter are important prognostic factors. We describe 6 cases of OPLL of the cervical spine seen at Westmead Hospital between 1979 and 1994. Of the 4 patients presenting with disabling compressive myelopathy, 3 made significant recovery following surgical decompression. Characteristic plain film features manifesting as a dense calcified linear structure along the course of the posterior longitudinal ligament (PLL) were present in 5 patients, including 1 who was asymptomatic. Computed tomography (CT) was invaluable in demonstrating the full extent of the disease in all 5 symptomatic patients. Magnetic resonance imaging (MRI) was helpful in excluding myelomalacia in 2 patients prior to successful surgery. The myelopathy caused by cervical OPLL remains rare, affecting mainly middle aged males of Asiatic and European extraction.