CNS Superficial Siderosis Mimicking a Motor Neuron Disease

Abstract

Superficial siderosis of the central nervous system (SS-CNS) is a rare condition characterized by a hemosiderin accumulation along the subpial surfaces and arises from an intermittent chronic bleeding in the subarachnoid space usually as a result of a chronic subarachnoid hemorrhage by trauma, vascular malformations, CNS tumors, or cerebral amyloid angiopathy (CAA). We present a 61-year-old male with a 12-year history of limb weakness, muscle wasting, cramps, clumsiness, progressive unsteady gait, and fine motor impairments. His medical history included the resection of a left parietal meningioma and a myxopapillary ependymoma near the conus terminalis (L3/4) at the age of 51 years. The clinical examination revealed a motor neuron syndrome with a clear bilateral wasting of the hand muscles, a diffuse atrophy of the shoulder and calf muscles, and a weakness of the arms, fingers, hips, and feet. Deep tendon reflexes were symmetrically briskly hyperactive. Standing and walking were only possible with a support. Magnetic resonance imaging of the entire neuroaxis showed progressive severe cerebral, brainstem, and spinal superficial siderosis in form of extensive hypointensities on T2-weighted gradient-echo images and susceptibility-weighted sequences. Despite a successful neurosurgical removal of the tumors and delaed medical treatment with an iron chelator for one year, we observed no clinical recovery or stability in our patient, making this case unique, and suggesting an irreversible neurodegenerative process. This case reinforces the need of including SS-CNS in the list of amyotrophic lateral sclerosis (ALS)-mimics and demonstrates the fundamental use of a complete neuraxial MRI investigation on evaluating possible ALS cases.

Keywords: ALS-mimics; case report; hemosiderin accumulation; motoneuron disease; spinal MRI; superficial siderosis.

Figure 1

Brain and spinal magnetic resonance imaging (MRI). (A) Coronal T2-weighted imaging showing left parietal meningioma; (B) sagittal T2-weighted imaging using Spectral Attenuated Inversion Recovery (SPAIR) of a myxopapillary ependymoma near the conus terminalis (L3/4); (C) T2-weighted images of cerebellum and brainstem showing superficial siderosis.

Figure 2

Follow-up brain and spinal MRI showing severe SS-CNS. (A) Susceptibility weighted transverse image SWI showing severe cortical and periventricular SS; (B) SWI of mesencephalic structures; (C) SWI of cervical spinal cord; (D) T2-weighted gradient-echo sagittal images of cervical spinal cord showing severe spinal SS.