Scar Dancing Syndrome: Peripheral Trauma Induced Involuntary Hyperkinesia around Surgical Incision

ABSTRACT

Background

Peripherally induced movement disorders represent a rare and debated complication of peripheral trauma. It is difficult to determine a causal relationship between peripheral injuries and subsequent movement disorders.

Cases

Here, we introduce and characterize four patients with post‐surgical scar‐associated movement disorders, a peripherally‐induced rippling movement disorder confined to the muscles just under a long surgical incision scar, appearing weeks to months after surgery. This novel ‘scar dancing’ syndrome does not spread to adjacent muscles and persists during sleep.

Conclusion

Scar dancing syndrome expands the phenotypic spectrum of peripherally induced movement disorders, in which movement disorder is confined to a long surgical incision site.

Peripherally induced movement disorder (PIMD) is defined as involuntary movements caused by trauma to the body outside of the central nervous system (CNS). The phenomenology of PIMD encompasses several types of hyperkinetic and hypokinetic movement disorders. The abnormal movements are thought to originate as muscle contractions that spread to adjacent muscle groups. More than 70% of PIMDs involve the neck/shoulder, arm, or leg. ¹ , ² In the absence of identifiable/deterministic lesions of origin, however, it is difficult to determine a causal relationship between peripheral injuries and subsequent movement disorders. Thus, this case series presents four patients with scar movement disorder after surgery: a novel PIMD that originates at a surgical incision site and does not spread to adjacent muscles and thus is clearly directly related to peripheral trauma.

Case Series

Case 1

A right‐handed 67‐year‐old woman with no neurological family history was referred to our department with an 18‐month history of dorsal neuropathic pain and progressive abnormal movements that started 2 weeks after back surgery for multiple rib fractures. Examination showed repetitive, semirhythmic writhing and jerky contractions of the left latissimus dorsi muscle along the surgical scar (Video 1). No significant abnormalities were found on thoracic magnetic resonance imaging (MRI). Needle electromyography (EMG) revealed frequent potential bursts of grouped, normal motor unit potentials (MUP) firing at 1 to 3 Hz of the involuntary motor unit of the left latissimus dorsi, with a maximum amplitude of 0.8 mV. The discharges were arrhythmical and highly unpredictable (Video 2). No exacerbating factors were known, though the involuntary movements did occur, with partial reduction of amplitude, during non‐rapid eye movement sleep and rapid eye movement sleep as assessed by video polysomnography. The involuntary movements were not influenced by distraction and voluntary movements. Multiple medications were ineffective, and in the end, 100 units of botulinum toxin A (BoNT‐A) were injected into the latissimus dorsi with slight improvement in pain and abnormal movements for the next 2 months.

Video 1.

Patient 1 with abnormal contractions of the left latissimus dorsi muscle along the surgical scar.

Video 2.

Surface EMG of case 1 showing potential bursts of the involuntary motor unit in the left latissimus dorsi.

Case 2

A 52‐year‐old man presented with a 3‐year history of dorsal neuropathic pain and progressive abnormal movements that surrounded a surgical scar on the left back and started 11 months after radical resection of an esophageal carcinoma (Video 3). EMG revealed intermittent, semirhythmic, 5‐ to 20‐ms bursts of grouped, normal MUP firing at 3 to 7 Hz in left latissimus dorsi (Video 4). Examination revealed sustained and rippling left latissimus dorsi contractions that persisted during sleep. The involuntary movements were not influenced by distraction with motor tasks, and suggestibility was not present. BoNT‐A 100 units administered to the left latissimus dorsi, improved the pain and movements (Video 5).

Video 3.

Patient 2 with abnormal scar movement on the left back.

Video 4.

Surface EMG of case 2 showing potential bursts of the involuntary motor unit in the left latissimus dorsi.

Video 5.

Patient 2 treated with BoNT‐A injection has a relief of the abnormal movement.

Case 3

A 62‐year‐old woman presented with a 20‐year history of painless involuntary movements over the right lateral neck region that began 2 months after a total thyroidectomy and remained persistent but stable after onset. Neurological examination showed jerking movements surrounding the sternocleidomastoid muscle (Video 6). Sensorimotor examination and cervical and thoracic spine MRI showed no visible abnormalities. No exacerbating factors were known. The abnormal movements did not exhibit significant changes during speaking or when sticking out the tongue. Thorough psychiatric assessment showed no evidence of psychiatric illness or psychotropic medications use. Her symptoms failed to improve despite treatment with BoNT‐A or other medications.

Video 6.

Patient 3 with abnormal movement over the right lateral neck region surrounding the surgical scar.

Case 4

A 58‐year‐old woman presented with a 1‐year history of painless, involuntary, slow, rippling muscle contractions that occurred at a surgical incision site on the right back and started 1 month after lung cancer surgery. She had no family history of movement disorders and had not been prescribed psychotropic medications. The contraction was enhanced during standing and walking, and relieved in the recumbent and supine positions (Video 7). EMG revealed tonic activity of right latissimus dorsi muscle with bursts of grouped, normal MUP firing semirhythmically at 0.5 to 10 Hz (Video 8). The movements were intermittent, occurring throughout the day, but disappeared during sleep. Multiple medications and an injection of BoNT‐A were not effective.

Video 7.

Patient 4 with muscle contractions at a surgical incision site on the right back after lung cancer surgery.

Video 8.

Surface EMG of case 4 showing potential bursts of the involuntary motor unit surrounding the right latissimus dorsi muscle.

Discussion

The concept of peripheral injury leading to centrally‐mediated movement disorders has always been controversial and poorly understood, and the rarity of PIMD further hinders the investigation of this controversial condition. Recognized PIMDs include the painful (painless) legs moving toes syndrome, postamputation dyskinesias, and belly dancer's dyskinesias. ³ A recent report described a novel PIMD: dancing dorsal quadrilaterals, characterized by neuropathic pain preceding a regional movement disorder following soft tissue or nerve injury. ⁴ We introduce and characterize scar dancing syndrome, a novel PIMD that occurs around long surgical incision sites, affects muscles just under the scar, and does not spread to adjacent muscles.

To our knowledge, these are the first reported cases of scar dancing syndrome due to a long incision lesion. Our cases have three remarkable features: (1) the singularity of the hyperkinesia surrounding the scar which may occur with or without pain, (2) a possible temporal link (less than 1 year) between the onset of the hyperkinesia and reinnervation of the motor unit within the surgical incision, (3) the involvement of muscles just under the scar with long surgical incisions (more than 5 cm).

Our diagnosis is in accord with Cardoso and Jankovic's 1995 diagnostic criteria for PIMD, ⁵ based on clinical characteristics, the presence of EMG abnormalities, and persistence of the movement disorder with distraction and attention. In all our patients, the hyperkinesia was anatomically related to the scar, and onset was temporally related to the surgery – within 1 year in all four cases. Given the chronology of events and the attack site, the etiology in our cases is, convincingly, a direct relationship between the peripheral trauma and the abnormal movement. To the best of our knowledge, this research is the first to report a surgery‐induced scar movement disorder; a literature review on PIMD after surgery did not reveal any cases similar to ours (Table 1). In some regards, the development of the movement disorder resembles belly dancer's dyskinesia and dancing dorsal quadrilaterals following surgical injury, ⁴ , ⁶ but scar dancing syndrome is distinct in that the dancing muscles are confined to the surgical incision site and show a pattern of movement disorder with an involuntary generator. In addition, while the movement associated with dancing dorsal quadrilaterals ceases during sleep, ⁴ our first two cases had documented abnormal movements during sleep.

TABLE 1.

Published case series of movement disorders after surgery

Reference	Demographics (Age/Sex)	Surgical procedure	Location	Onset after surgery	Pain	Treatment (effective, +/−)
Park KW, 2020 10	25, M; 38, M	Pulmonary endarterectomy		Immediately; 10 days	NA	Meds (−)
	48, M	Repair of thoracic aortic dissection		1 month	NA	Meds (−)
Sardana V, 2019 11	28, M	Dorsal spine fixation surgery (D5‐D8)	Lower trunk and limb	2 years	Yes	Meds (−)
Lizarraga KJ, 2019 13	mean age 50s; (2F, 2 M)	Spine instrumentation complicated by misalignment	Dorsal quadrilaterals muscles	4 months to 2 years	Yes	BoNT‐A (+/−) Meds (−)
Takemoto M, 2006 13	45, M	Cervical anterior corpectomy	Neck	3 months	Yes	BoNT‐A (+)
Capelle HH, 2004 14	mean age 50s; (3F, 3 M)	Cervical/lumbar disc herniation	Arms or legs	1 day to 12 months	Yes	NA
Cossu G, 2004 15	39, M	Lipoma resection from left posterior triangle of the neck	Left shoulder	1 year	No	BoNT‐A (+)
Becker G, 2002 16	mean age 40s; (6F, 7 M)	Cervical disc herniations	Shoulder girdle	Mean 2.4 years	Yes	NA
Bötzel K, 1999 17	58, M	Esophageal carcinoma resection	Right shoulder	3 months	Yes	Meds (−)
Sankhla C, 1998 18	mean age 50s; (3F, 1 M)	Gum or oral surgery; Temporomandibular joint arthroscopic surgery		3–10 days	Yes	BoNT‐A (+)
Ghika J, 1997 19	mean age 30s; (1F, 3 M)	Lumbar disc herniation repair	Trunk or leg	3 weeks to 15 years	No	BoNT‐A (−) Clonazepam (+/−)
Iliceto G, 1990 20	58, M	Cholecystectomy	Abdomen	15 months	NA	Meds (−)
	67, F	Cystoscopy	Abdomen	Immediately	Yes	Meds (−)
Jankovic J, 1988 21	mean age 30s; (1F, 2 M)	Laminectomy	Arms or legs	1 day to 9 months	NA	Meds (−)
	17, F	Hip surgery	Left foot	1 month	NA	Meds (−)

The references can be found in the online supplement.

The pathophysiology of PIMD remains unclear. PIMD often is associated with pain (86%) and other sensory phenomena, including complex regional pain syndrome (CRPS). ¹ The prominent feature of pain calls attention to the sensory system as a potential pathophysiological key. It has been postulated that the abnormal movements are due to a dysfunction of inhibitory spinal interneurons or structural reorganization of local neuronal circuits. Trauma may alter sensory input from the site of impact to the CNS, eventually leading to spinal or supraspinal reorganization and the emergence of an abnormal motor output. ⁷ , ⁸ However, not all of our patients had pain to explain such movements. CRPS and non‐CRPS patients are thought to differ in the types of trauma and locations of the movement disorders. ¹ The diagnostic criteria of PIMD do not include lesions on brain imaging, so any lesions theoretically should be in “unrelated” areas of the CNS, though it is not known whether lesions may pre‐dispose to abnormal movements. In our patients, we suppose that the prime mover lies in the peripheral, not central nervous system. The abnormal movements persistence during sleep in most of our cases supports that these movements might be triggered at peripheral level. It might reflect peripheral nerve hyperexcitability due to lesion of distal nerve terminals or abnormal reinnervation with ephaptic activation of nerve terminal. What is more, the abnormal movements were confined to the muscles innervated by the same nerve involved in the scar tissue and did not involve other muscles. The electrical instability of the intramuscular motor nerve branch may predispose to or pave the way for the hyperkinesia. Given the presumed rarity of scar dancing syndrome, there may be genetic susceptibility and other important predisposing factors that are not apparent in this small case series alone.

The management of PIMD is extremely challenging. Most cases of PIMD are refractory to various medical and surgical treatment modalities. No treatment modality has been proven consistently effective. Botulinum toxin is the most commonly used treatment for symptomatic cases, but with a success rate of only 20%. ¹ , ⁹ Interestingly, the first two of our cases both suffered from neuropathic pain that improved with botulinum toxin, so we posit that it may be suitable for scar dancing patients who have neuropathic pain. Further studies are needed to confirm the effectiveness of botulinum toxin injections in such patients.

In conclusion, our case series expands the phenotypic spectrum of PIMD by providing four visual examples of scar dancing syndrome, in which hyperkinesia is confined to a long surgical incision site. May further reports, particularly with regard to neuroimaging findings in these patients, continue to uncover the pathogenic mechanism.

Author Roles

(1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique.

X.Y.: 1A, 1B, 1C, 2C, 3A

H.L.: 1B, 2A, 3B

M.M: 1A, 2C, 3B

X.W.: 1A, 2A, 2C, 3B

Y.W.: 1A, 2A, 2C, 3B

Disclosures

Ethical Compliance Statement: The authors confirm that the approval of an institutional review board was not required for this work. 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. Permission were obtained from the patients to have access to their clinical records, write the manuscript and use their videos obtained.

Funding Sources and Conflicts of Interest: This study was supported by the National Natural Science Foundation of China [Grant number 81870887 to YW Wu, Grant number 81971074 to XH Wan]. The authors report no conflicts of interest.

Financial Disclosures for Previous 12 Months: M.M is supported by the NINDS Intramural Program.