Abstract
Superficial intracranial siderosis (SIS) is a rare and often unrecognized disorder of the central nervous system (CNS) characterized by progressive neuronal degeneration resulting from chronic subarachnoid bleeding. Hemoglobin accumulates in the subarachnoid space where it is metabolized to hemosiderin and deposited in the subpial layer of those parts of the CNS adjacent to the cerebrospinal fluid with predilection for inter alia the cerebellum and cranial nerves I, II and VIII. Hemosiderin deposits lead to neuronal damage, reactive gliosis, and demyelination. Often the hemorrhage is occult and no bleeding source can be detected. Classic symptoms are sensorineural deafness, cerebellar ataxia and pyramidal signs [1]. Ophthalmic symptoms such as nystagmus have also been reported. Visual dysfunction however is not a recognized feature of SIS. Indeed, patients in an advanced stage have been shown to have normal optic nerve function [2]. Polidori et al documented a case of optic nerve dysfunction in a patient with SIS and concomitant glaucoma [3]. In 2008 Koeppen et al postulated that visual failure solely due to SIS does not occur [4]. But Painter et al reported two cases of SIS with strong evidence of optic nerve dysfunction and one postmortem case of histological findings of iron deposition and associated demyelination in the optic nerve [5]. Magnetic resonance imaging (MRI) is the diagnostic method of choice showing features of hemosiderin accumulation on CNS surfaces [4].
Enz, T J