IntroductionSacral extradural arachnoid cysts are rare. When present, they produce low back pain and pain in the perineal region, which is aggravated by Valsalva maneuvers and relieved by lying down. A high index of suspicion is required to diagnose this condition. To date, 41 cases have been reported in the English language literature (Table 1).
Case reportA 25-year-old man presented with a 2-year history of pain over the low back and perineal region, which had become severe 1 month prior to admission. The pain was aggravated by standing, walking and straining, and was relieved partially by lying down in the prone position. The patient also complained of numbness of both lower limbs on prolonged standing or walking, which was relieved by lying down. There was no other positive history. Examination revealed normal higher functions and cranial nerves. The patient had weakness of the extensor hallucis longus on both sides, left more than right. There was also tenderness over the upper sacral region. Bladder, bowel and sexual functions were normal. There were no other focal neurological deficits. Plain radiographs of the lumbosacral region revealed a suspicious bony erosion in the midsacral region. Magnetic resonance imaging (MRI) revealed a cystic lesion opposite the second and third sacral segments, which was isointense to cerebrospinal fluid (CSF) on T1-and T2-weighted images (Fig. 1). There was evidence of communication of the cyst with the caudal end of the thecal sac. There was no communication with the pelvis. Scalloping of the sacrum was evident. At surgery, laminectomy of S1-S4 was done, and a large, thin-walled bluish cystic mass containing CSF was encountered, which was opened. The cystic mass was found to be communicating with the thecal sac through a defect in the theca. The fistulous communication was obliterated and the defect in the theca was closed with purse-string sutures. Postoperatively, the patient noted marked relief of pain and did not have numbness while standing and walking. Two years following surgery, the patient was neurologically normal without any deficits.
DiscussionThe term "occult sacral meningocele" was first introduced by Enderle in 1932 [19]. It has come to mean a sac composed of fibrous tissue resembling dura mater that is usually lined by arachnoid, lies within an enlarged sacral spinal canal, and is attached to the distal termiAbstract Sacral extradural arachnoid cysts are rare. The clinical and radiological features of this condition are characteristic. One such rare case with low back and perineal pain is presented and the literature is reviewed. This patient presented with pain in the low back and perineal region, which was aggravated by standing, walking and straining. The patient also had numbness in both lower limbs, precipitated by standing and walking. Both the symptoms were relieved by lying down. Magnetic resonance imaging (MRI) revealed a sacral extradural arachnoid cyst. Sacral laminectomy with opening of the arachnoid cyst and ligation of the fistulous tract was ...
