[Congenital extradural cyst causing a 30-year history of myelopathy with long-term remission]

We reported a peculiar case of a patient with a thoracic extradural cyst, who had a 30-year history of thoracic-myelopathy with a very long-term remission. A 42-year-old male was admitted to our hospital complaining of gait disturbance and hypesthesia of his bilateral lower limbs. Neurological examination revealed that he had spastic paraparesis and hypesthesia of all sensory modalities below Th11/12 dermatomes. Investigation of his past history disclosed that he had experienced gait disturbance due to paraplegia 29 years previously and had been able to move only with the aid of wheel-chairs. However these signs had resolved themselves gradually in a period of 3 years, and after that he had been able to live almost without any neurological handicaps until the recent appearance of weakness in both of his legs. Neuroradiological study revealed that plain X-Ps of the thoracic spine showed thinning of the pedicles and widening of the interpedicular distances between Th4-Th7 vertebrae. The old iodine contrast media injected 29 years previously for myelography in an other hospital was also observed. MRI showed a dorsal cystic mass compressing the thoracic spinal cord and subarachnoid space. Myelography showed also that the spinal cord and subarachnoid space were compressed anteriorly between the level of Th3 to Th7 by the dorsal mass. CT myelography disclosed that soon after the injection of contrast media a small part of the cyst was visualized as having direct communication with the subarachnoid space. The contrast media penetrated the major part of the cyst only 19 hours after its injection.(ABSTRACT TRUNCATED AT 250 WORDS)