Spontaneous hematomas of the iliacus muscle are rare lesions and these are seen in individuals receiving anticoagulation therapy or patients with blood dyscrasias such as hemophilia. It can cause femoral neuropathy and resultant pain and paralysis. Although there is no clear consensus for the treatment of femoral neuropathy from iliacus muscle hematomas, delays in the surgical evacuation of hematoma for decompression of the femoral nerve can lead to a prolonged or permanent disability. We report here on a rare case of a spontaneous iliacus muscle hematoma that caused femoral neuropathy in a patient who was taking warfarin for occlusive vascular disease and we discuss the treatment.

A 75-year-old woman was transferred to the emergency room, complaining of severe headache of sudden onset, low back pain, nausea, and dizziness. She was alert and oriented. She had signs of meningeal irritation, but the neurological examination was otherwise normal. Brain CT revealed SAH in the right Sylvian fissure and basal cistern. Three-dimensional brain CT angiography showed a right middle cerebral artery aneurysm. Emergent craniotomy via right-sided pterional approach without installation of lumbar cerebrospinal fluid (CSF) drain and neck clipping of the aneurysm was performed uneventfully under general anesthesia.Following operation, she complained of worsening pain in the lumbosacral, buttock, and the posterior aspect of the right thigh. The pain was intermittent at onset and exacerbated by sitting, walking, and coughing. Bed rest relieved the pain. She had no history of previous back problems, or recent trauma. On neurological examination, no abnormal findings were found. Lumbar spine MR images 2 weeks postoperatively showed a 15×15×16 mm Tarlov cyst at the S2 level affecting the right S2 root with high signal intensity in T2 and T1 images, suggestive of bleeding within the cyst and a so-called "dark disc" at multilevel lumbar spines (Fig. 1). She suffered from pain despite analgesics and physical therapy for 2 weeks after MR imaging.CT-guided aspiration of the cyst was performed and approximately 1 cc of old blood was aspirated (Fig. 2). Her pain was relieved immediately after aspiration and she had only mild dis- INTRODUCTIONTarlov or perineurial cysts were first described by Tarlov in 1938 as an incidental finding during autopsy studies of the filum terminale. The cysts arise at the junction of the dorsal root ganglion and the posterior nerve root and develop between the endoneurium and perineurium and are most often found in the sacral region 2,12) . The prevalence of perineurial cysts has been reported in 9% of autopsy specimens before the magnetic resonance (MR) era and estimated to be approximately 1.5-4.6% in large series using MR images 4,9,10) . Although cases of Tarlov cysts causing coccydynia, sacral pain, sacral radiculopathies, and sacral insufficiency fractures have been reported, most Tarlov cysts remain asymptomatic throughout the patient's life 1,4) . Most of the cysts are found incidentally during computed tomography (CT) or MR imaging for other reasons and 13-22% of the patients with the cysts had symptoms 4,9) . Why some of the Tarlov cysts progress to cause symptoms is unclear. These cysts may become symptomatic by local compression of adjacent bone or displacing nerve roots, if they become large 1,4) . Hemorrhage has been suggested as one of the possible causes of these cysts and trauma with resultant hemorrhage into the subarachnoid space has been suggested as an origin of these cysts 6,7,12) . However, symptomatic Tarlov cysts related to spontaneous SAH have not been reported. We report a J Korean Neurosurg Soc 50 : 123-125, 2011 http://dx.doi.org/10.3340/jkns.2011 Copyright ©...