From: Spinal-generated movement disorders: a clinical review
SGMDs | Phenomenology | Pathophysiology | Main clinical features | Investigations | Treatment |
---|---|---|---|---|---|
Spinal segmental myoclonus (SSM) | Myoclonus | • Loss of inhibition of spinal interneurons → hyperexcitation of anterior horn cells | • Jerks of 1 or 2 limbs • Rhythmic or semi-rhythmic • Generally not stimulus-sensitive | • MRI of the spinal cord | • Rx of specific etiologies. • CLZ, VPA or LVT for symptomatic Rx |
Propriospinal myoclonus (PSM) | Myoclonus | • Possible defects in propriospinal pathways (not yet proven in humans) • Psychogenic etiology also proposed | • Slow truncal jerking • Flexion more common than extension • Stimulus-sensitive, but longer latency than cortical myoclonus | • MRI of the spinal cord • EP testing | • Rx of specific etiologies in 2° forms • CLZ or VPA for symptomatic Rx |
Orthostatic tremor (OT) | Tremor | • Unclear • Proposed tremor generators: brainstem, thalamus, and spinal cord • 1° and 2° (OT-plus) forms exist | • 13–18 Hz; in legs and trunk • Present when standing but not walking • Subjective unsteadiness; tremor may not be visible • Improved when lightly touching a table or wall • “Helicopter sign” | • EP testing • MRI of the brain or spinal cord (if exam is abnormal and 2° OT is suspected) | • Mainly CLZ or GBP • L-dopa or DA may be used in cases with concomitant parkinsonism |
Paroxysmal tonic spasms in multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) | Dystonia | • Ephaptic transmission between partially-demyelinated axons anywhere in central nervous system • Common locations: contralateral cerebral peduncle, internal capsule, and spinal cord | • Painful; involves unilateral arm or leg • Typically non-kinesigenic • Last several seconds to minutes • May involve ipsilateral face • Aggravated by hyperventilation • Can be initial presentation of MS | • MRI of the brain and spinal cord • Other MS/NMOSD work-up including CSF studies | • CBZ or acetazolamide |
Stiff person syndrome (SPS) and its variants | Stiffness | • Impaired spinal GABAergic and glycinergic inhibitory circuits → CMUA • Supraspinal mechanisms proposed | • Classic form: stiffness of the trunk and legs, hyperlordotic gait • Stiff limb variant: involves only 1–2 limbs | • Ab testing (serum anti-GAD, anti-amphiphysin; less commonly anti-glycine or GABAA receptor) • Malignancy work-up | • Rx of specific etiology if any • Immunosuppressive Rx: steroid, IVIg, and/or PLEX; chronic oral agents such as MMF, AZA and CYC • BZDs for symptomatic Rx |
Progressive encephalomyelitis with rigidity and myoclonus (a variant of SPS) | Stiffness, myoclonus | • Loss of spinal inhibitory interneurons • Brainstem also involved | • Myoclonic jerks of the trunk, limbs and cranial muscles • +/− Nystagmus, oculomotor abnormalities, dysarthria and dysphagia | • Ab testing (serum and CSF anti-GAD, anti-glycine receptor, anti-DPPX) • MRI of the spinal cord and brainstem • CSF studies may be required | • Rx of specific etiology if any • Immunosuppressive Rx as in SPS |
Movements in brain death and automatic stepping* | Spinal reflexes | • Disconnection of supraspinal control → disinhibition of the spinal reflexes • Some proposed released phylogenetically primitive patterns • Automatic stepping: spinal automatism from spinal CPG | • 2 types (examples shown) - Automatisms (abdominal contraction, undulating toe movements) - Reflexes (after neck flexion, finger pinching or testing Babinski sign) • Automatic stepping reported in a near brain-dead patient | • Confirmation of brain death (physical exam, apnea testing or TCD, etc.) | • Family reassurance |
Painful legs-moving toes syndrome (PLMT) | Miscellaneous | • Unknown • Proposed mechanism: peripheral nerve pathology → 2° impairment in spinal and/or supraspinal controls, and central sensitization | • Slow 1–2 Hz, athetoid-like • Involves fingers or toes • Moves in vertical and/or horizontal planes • Pain usually the most debilitating symptom • Painless form present | • Work-up for associated neuropathies or radiculopathies depending on clinical context • MRI of the spinal cord rarely required | • Rx of concomitant diseases such as neuropathies • GBP or PGB • Others (case reports): baclofen, CBZ, BZD, TCA, SCS, epidural block, sympathetic blockade, TENS, BoNT |