Superficial Siderosis Related to a Thoracic Disc Herniation with Associated Dural Injury

Superficial siderosis (SS) of the central nervous system leads to gradual neurological deterioration characterized by sensorineural hearing loss, cerebellar ataxia, and myelopathy [1,2]. SS has a prevalence of approximately 0.7% in the general population [3]. Males appear to be affected more often than females by a 2:1 ratio, and the average age of presentation is between the 5th and 6th decades of life [1]. Chronic bleeding into the subarachnoid space can cause deposition of hemosiderin in neuronal tissues and the characteristic hypointensity seen on T2-weighted magnetic resonance imaging (MRI) [1,2]. Causes of bleeding include a past history of intradural surgery, head/back trauma, central nervous system tumors, arteriovenous malformation, nerve root avulsion, dural injury [1,2], and cerebral amyloid angiopathy [4]. SS has been rarely reported in association with dural defects caused by protruding intervertebral discs [5,6]. We present an unusual case of chronic pial siderosis related to a thoracic disc herniation with associated dural injury. Heightened suspicion and appropriate use of imaging can lead to diagnosis and prompt treatment of this condition. A 66-year-old, right-handed man presented to our neurology clinic with a four-year history of leg weakness and progressive gait impairment. Symptoms progressed over time, and he started to use a cane 6 months previously. The patient also reported bilateral hearing loss and urinary incontinence. He denied tremor, fasciculations, back pain, falls, dysphagia, or dysarthria. His past medical history was otherwise unremarkable. Neurological exam revealed bilateral sensorineural hypoacusis. Muscle strength was 5/5 in both upper extremities and 4/5 in the lower extremities. Deep tendon reflexes were mildly hyperactive in the lower extremities while normal in the upper limbs. The plantar reflex was extensor on the right and flexor on the left. Sensory examination was normal. The patient had a spastic– ataxic gait with bilateral foot drop. Complete blood count, serum glucose, and electrolytes were normal. A lumbar puncture was performed with an opening pressure of 7 cm of water. Cerebrospinal fluid (CSF) was xanthochromic and had hyperproteinorachia (59.8 mg/dL [normal < 50 mg/dL]), 2 leukocytes/mm, 117 erythrocytes/mm, and a normal glucose. A brain MRI showed extensive hypointensity around the brainstem and along the cerebellar folia (Figure 1A) as well as within the cerebral fissures (Figure 1B). Cervical (Figure 1C) and thoracic (Figure 2A) MRIs also showed hypointensity along the entire pial surface of the spinal cord and a disc herniation at the T8–T9 level. Cerebral and spinal angiography showed no signs of extravasation of contrast agent representing bleeding. A dynamic CT myelogram was also performed and showed a ventral dural defect at the level of the thoracic disc herniation (Figure 2B). These findings were consistent with chronic pial siderosis related to a thoracic disc herniation with associated dural injury. Physical therapy was started, and surgical repair of the dural defect was offered but declined by the patient. The patient has remained stable without increasing disability after 6 months of follow-up. Repeat MRI 6 months later showed persistence of hemosiderin deposits around central nervous system (CNS) structures. The classic triad of sensorineural hearing loss, cerebellar ataxia, and myelopathy is present in 39% of cases [1]. Clinical findings