Case reports:
Case 1: A 63-year-old man from a rural region where people regularly consume well water with fluoride dust, presented to our department with quadriplegia and urinary incontinence. His symptoms started insidiously with pain in the joints and the back. Then, he started having weakness of upper and lower limbs with difficulty in walking. Clinical examination revealed stiffness of the neck and back, a spastic quadriplegia with stretch reflex hyperactivity and presence of Babinski sign. Blood tests were normal. On X-rays of cervical and thoracic spine, a diffuse osteocondensation was found. A cervical CT revealed a spinal cord compression by exuberant osteophytosis and ossification of longitudinal ligament at cervical levels (C4-C7). MRI revealed signs of myelopathy with high signal intensity T2 of the spinal cord (Fig.1) . Only symptoms treatment (analgesic and non-steroidal anti-inflammatory drugs) was proposed for this patient. Surgical decompression was discussed but not performed because of the high-risk-surgery.
Case 2: A 70-year-old man from south of Tunisia, presented to our department with 1-year history of weakness of upper and lower limbs with urinary incontinence. Clinical examination revealed a severe spastic quadriparesis, a pyramidal syndrome with a sensory level (T4) accompanied by back pain with limited spinal mobility. In addition, brownish mottling was observed on his teeth. Plain X-rays of cervical and thoracic spine and computed tomography (CT) revealed diffuse osteosclerosis with exuberant osteophytosis and ossification of the posterior longitudinal ligament. In addition, an ossification of interosseous membranes on forearms and legs-X-rays was found(Fig.2) . Biological tests were normal. Magnetic resonance imaging (MRI) revealed a spinal cord compression due to ossification of the ligamentum flavum and posterior longitudinal ligament at the cervical level (C4-C6) with high signal intensity (T2) of the spinal cord.
Case 3: A 70-year-old-man from a rural area (Sidi Bouzid, Tunisia) presented to our department with 4-months history of chronic weakness of lower limbs with urinary incontinence accompanied by neck and lower back pain. On examination, a spastic quadriparesis with a pyramidal syndrome and Babinski sign were revealed. X-rays showed increased bone density with calcification of ligaments, muscular attachment (on pelvis and spine) and interosseous membranes. MRI revealed a spinal cord compression due to ossification of posterior longitudinal ligament at the cervical level. Decompressive laminectomy was proposed for this patient.