Abdominal Segmental Myoclonus Resembling Belly Dancer Dyskinesia: An Autopsy‐Proven Case

“Belly dancer dyskinesia (BDD)” is a descriptive term for involuntary, undulating abdominal movements with diverse reported etiologies, leading to debate about its pathophysiology. Spinal myoclonus is attributed to the disinhibition of spinal central pattern generators (CPGs).1 While some argue for a clear distinction, significant phenomenological overlap exists, suggesting that it may represent a clinical mechanistic spectrum.2, 3 However, this hypothesis lacks definitive histopathological evidence. We present the first autopsy-proven case of BDD-like hyperkinetic movement disorder, providing direct evidence that the generator is localized in a severely inflamed brainstem and spinal cord. A 59-year-old man with no known immunodeficiency was admitted with a three-day history of progressive confusion. His examination was remarkable for continuous, rhythmic, 2–3 Hz wave-like contractions of the entire abdominal wall, phenomenologically consistent with BDD (Video 1). Critically, these movements persisted unabated under deep sedation using anti-seizure medications, benzodiazepines, and propofol. Cerebrospinal fluid (CSF) analysis revealed lymphocytic pleocytosis (125 cells/μL) and elevated protein levels, consistent with meningoencephalitis. His neurological status rapidly declined, requiring mechanical ventilation, and he died of sudden cardiac arrhythmia on day five. A postmortem CSF culture grew Mycobacterium intracellulare; however, as this was a single finding, its pathogenic role was uncertain, and contamination could not be definitively excluded. A comprehensive neuropathological examination was pivotal. Macroscopically, the brain and spinal cord appeared edematous. Microscopic examination revealed extensive lymphohistiocytic inflammatory infiltrates throughout the leptomeninges of the brainstem and the entire spinal cord. Lymphocytic infiltration with edema also involved subpial white matter that is anterior corticospinal, spinothalamic and spinocerebellar tracts, posterior funiculus (Fig. 1B). Lymphocytic infiltration cuffing along vascular externa extended deep into the parenchyma (Fig. 1C). Perivascular lymphocytic cuffing of spinal cord was prominent even in central gray matter and focally surrounded by spongiosis (Fig. 1A) though degeneration of neuronal body wasn't definitive. This distribution involves the anatomical location of the internuncial fibers and propriospinal neurons that constitute the spinal CPGs, rather than the primary somatic motoneurons of the limbs (Fig. 1A,C). The pontomedullary reticular formation was also affected by spongiotic change around perivascular lymphocytic cuffing. In contrast, the cerebral cortex, basal ganglia, and cerebellum were largely unaffected. This case uniquely correlated a clinical phenomenon with precise anatomical pathology. The persistence of movement under deep sedation effectively ruled out a cortical origin. Our pathological findings provide a direct anatomical substrate for this clinical observation, demonstrating severe inflammation and neuronal destruction in the brainstem-spinal cord networks known to contain CPGs. We postulate that the inflammatory process causes fatal disruption of supraspinal inhibitory pathways that normally regulate spinal CPGs. This disinhibition resulted in continuous, pathological, rhythmic motor output observed clinically. Our findings provide the first direct histopathological evidence that the BDD-like movements can be a manifestation of abdominal segmental myoclonus driven by a disordered brainstem-spinal cord CPG. This case supports the concept that these phenomena represent a spectrum of diseases unified by the disinhibition of intrinsic rhythmogenic circuits. This underscores that when a BDD-like phenotype is encountered, particularly with features suggestive of myoclonus, the structural etiology affecting the brainstem or spinal cord must be thoroughly investigated.4, 5 (1) Research project: A. Conception, B. Organization, C. Execution; (2) Manuscript: A. Writing of the first draft, B. Review and Critique. Y.T.: 1A, 1B, 1C, 2A, 2B. Y.N.: 1C, 2B. M.I.: 1C, 2B. K.N.: 2B. Y.S.: 2B. S.T.: 1C, 2B. Y.I.: 1C, 2B. H.I.: 1B, 2B. We thank Editage (www.editage.com) for English language editing. Ethical Compliance Statement: The authors confirm that the approval of an institutional review board was not required for this work. Informed consent for autopsy and for the publication of this case report, including clinical data and video, was obtained from the patient's next of kin. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. Funding Sources and Conflict of Interest: No specific funding was received for this work. The authors declare that there are no conflicts of interest relevant to this work. Financial Disclosures for the previous 12 months: The authors declare that there are no additional disclosures to report. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.