title: Distal bimelic amyotrophy (DBMA): Phenotypically distinct but identical on cervical spine MR imaging with brachial monomelic amyotrophy/Hirayama disease.
abstract: Our objective was to characterize the MR imaging features in a large and distinct series of distal bimelic amyotrophy (DBMA) from India. We utilized a retrospective and prospective study on 26 cases. Results demonstrated that upper limb distal muscle wasting and weakness was predominantly symmetrical in onset. Mean age at onset was 20.9 ± 7.0 years, mean duration 83.0 ± 102.6 months. MRI carried out in 22 patients with flexion studies showed forward displacement of posterior dura in 19 (86.4%). Crescent shaped epidural enhancement on contrast was seen in 20/24 cases (83.3%), and bilateral T2W hyperintensities of cord in17 (65.4%) - symmetrical in15 cases. Maximum hyperintensity was noted at C5-C6, C6-C7 levels. Cord atrophy was noted in 24 (92.3%) cases (most affected: C5-C6, C6-C7) - symmetrical atrophy in 21cases. Cervical spine straightening occurred in six (23.1%) cases and reversal of lordosis in 15 (57.7%). In conclusion, this study confirms that DBMA is phenotypically distinct but pathophysiologically the same as brachial monomelic amyotrophy (BMMA) on MR imaging. Typical MRI features were seen in all. It is important to differentiate this disorder from ALS, which could present at a younger age as often seen among Indians. The clinical and MR imaging features are highly suggestive that DBMA, as with BMMA/Hirayama disease, occurs due to dynamic alterations at the cervical spine level.
authors.affiliation: b Clinical Neurosciences, National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Veeramani
authors.initials: V
authors.lastname: Preethish-Kumar
authors.affiliation: a Department of Neurology , National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Atchayaram
authors.initials: A
authors.lastname: Nalini
authors.affiliation: a Department of Neurology , National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Ravinder-Jeet
authors.initials: RJ
authors.lastname: Singh
authors.affiliation: c Neuro Imaging and Interventional Radiology, National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Jitender
authors.initials: J
authors.lastname: Saini
authors.affiliation: c Neuro Imaging and Interventional Radiology, National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Chandrajit
authors.initials: C
authors.lastname: Prasad
authors.affiliation: b Clinical Neurosciences, National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Kiran
authors.initials: K
authors.lastname: Polavarapu
authors.affiliation: d Biostatistics, National Institute of Mental Health and Neurosciences , Bengaluru , India.
authors.forename: Kandavel
authors.initials: K
authors.lastname: Thennarasu
mesh_terms: D000293:Adolescent; D000328:Adult; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis*; D002574:Cervical Vertebrae / Q000473:pathology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007194:India; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D014897:Spinal Muscular Atrophies of Childhood / Q000175:diagnosis*
keywords: BMMA; DBMA; Hirayama disease; brachial monomelic amyotrophy; distal bimelic amyotrophy; flexion induced myelopathy; magnetic resonance imaging