Duropathy as a rare motor neuron disease mimic: from bibrachial amyotrophy to infratentorial superficial siderosis

Abstract

Background: Bibrachial amyotrophy associated with an extradural CSF collection and infratentorial superficial siderosis (SS) are rare conditions that may occasionally mimic ALS. Both disorders are assumed to be due to dural tears.

Case presentation: A 53-year-old man presented with a 7-year history of slowly progressive asymmetric bibrachial amyotrophy. Initially, a diagnosis of atypical motor neuron disease (MND) was made. At re-evaluation 11 years later, upper limb wasting and weakness had further progressed and were accompanied by sensorineural hearing loss. MRI of the brain and spine demonstrated extensive supra- and infratentorial SS (including the surface of the whole spinal cord) as well as a ventral longitudinal intraspinal fluid collection (VLISFC) extending along almost the entire thoracic spine. Osteodegenerative changes were observed at C5-C7 level, with osteophytes protruding posteriorly. The bony spurs at C6-C7 level were hypothesized to have lesioned the dura, causing a CSF leak and thus a VLISFC. Review of the MRI acquired at first evaluation showed that the VLISFC was already present at that time (actually beginning at C7 level), whereas the SS was not. 19 years after the onset of upper limb weakness, the patient additionally developed parkinsonism. Response to levodopa, brain scintigraphy with ¹²³I-ioflupane and brain MRI with nigrosome 1 evaluation were consistent with idiopathic Parkinson's disease (PD). On the latest follow-up 21 years after symptom onset, the VLISFC was unchanged, as were upper arm weakness and wasting.

Conclusions: Based on the long-term follow-up, we could establish that, while the evidence of the VLISFC was concomitant with the clinical presentation of upper limb amyotrophy and weakness, the radiological signs of SS appeared later. This suggests that SS was not per se the cause of the ALS-like clinical picture, but rather a long-term sequela of a dural leak. The latter was instead the causative lesion, giving rise to a VLISFC which compressed the cervical motor roots. Dural tears can actually cause several symptoms, and further studies are needed to elucidate the pathophysiological correlates of "duropathies". Finally, as iron metabolism has been implicated in PD, the co-occurrence of PD with SS deserves further investigation.

Keywords: ALS mimics; Bibrachial amyotrophy; Dural leak; Duropathy; Superficial siderosis; Ventral longitudinal intraspinal fluid collection.

Fig. 1

MRI images of July 2019. A: axial GRE image showing infratentorial hemosiderin deposition (pons (white arrow), cerebellar vermis (white asterisk), cortex of cerebellar hemispheres (white arrowhead)). B: axial GRE image showing supratentorial hemosiderin deposition (right temporal and insular cortex (white arrowhead), bilateral medial parieto-occipital cortex (white asterisk)). C: T2-TSE sagittal image of the cervical cord showing osteophytes and disc protrusions at C5-6-7 levels (white asterisks). D and E: T2-TSE sagittal images of the cervical and dorsal cord, respectively, showing hypointense rim of hemosiderin deposition along the entire length of the cord (white arrows) and a VLISFC extending from T2-T3 level to T11 level (white asterisks). F: axial T2-SPACE image at C6 level showing the hypointense rim of hemosiderin deposition on the cord surface (white arrow) but no signal alterations of the anterior horns. GRE, gradient-recalled echo. MRI, magnetic resonance imaging. TSE, turbo spin echo. VLISFC, ventral longitudinal intraspinal fluid collection

Fig. 2

MRI images of December 2008. A: sagittal T2-TSE image showing osteophytes at C5-6-7 levels (white asterisks) and the VLISFC beginning at C7 level (white arrowhead), but no rim of hemosiderin deposition along the surface of the cord. B: axial T2-me2d image at C6 level showing the VLISFC (white arrowhead) but no hemosiderin deposition on the cord surface. MRI, magnetic resonance imaging. TSE, turbo spin echo. VLISFC, ventral longitudinal intraspinal fluid collection

Fig. 3

MRI image of Agust 2021. SWI image showing bilateral absence of the hyperintense signal of nigrosome 1 (black arrowheads). MRI magnetic resonance imaging. SWI, susceptibility-weighted imaging

Fig. 4

MRI images of October 2022. Sagittal T2-TSE images of the cervical (A) and lumbar spine (B) showing persistence of the hypointense rim of hemosiderin along the surface of the cord (white arrows) as well as persistence of the VLISFC, beginning approximately at T2-T3 level (white asterisk in image A) and ending at T11 level (white asterisk in image B). MRI, magnetic resonance imaging. TSE, turbo spin echo