Objective: To report on two non-related cases of congenital mirror movements (CMM).

Background: Mirror movements (MM) are involuntary symmetrical movements of one side of the body that mirror intentional movements of the other side, making the person affected unable to perform a purely unimanual task. They are common in early childhood when motor mirroring is presumed to stem from incomplete myelination of the transcallosal tract and insufficient interhemispheric inhibition. Their persistence into adulthood is pathological and may occur either as an ‘essential’ movement disorder with no other neurological features (CMM) or as part of a syndrome (Kallmann, Joubert, Wildervanck, Klippel-Feil etc). Their re-emergence in later life (acquired MM) is commonly seen during the course of neurodegenerative diseases such as PD.

CMM is a very rare disorder, with an estimated prevalence of less than 1:1,000,000. The severity of the MM is defined on a scale from 0 (no MM) to 4 (MM equal to that observed in the intended hand). CMM is generally inherited in an autosomal dominant (AD) manner, with heterozygous pathogenic variants identified in about 35% of affected individuals/families in either the DCC or RAD51 gene. The identified genes have roles in axon guidance at the midline of the corticospinal tract.

Methods: Clinical and family history, examination, video assessment, blood tests to screen for syndromic causes of MM, smell test (UPSIT), brain and cervical spine MRI. Screening for mutations in DCC and RAD51 genes was performed through next-generation sequencing (NGS).

Results: Case 1 (M.B.) and case 2 (A.A.) were both otherwise healthy, right-handed 16 year-olds who had exhibited mirror movements of both hands since early childhood, which had become problematic as they had begun performing more complex bimanual tasks. There was no relevant family history; the clinical examination was unremarkable except for repetitive sustained MM of both hands in which the nonvolitional hand followed smoothly and closely the movements of the volitional hand (video). MM score was 3. Blood tests and olfaction were normal. M.B’s MRI revealed non-specific developmental changes in the brain, and A.A.’s neuroimaging showed no abnormalities. NGS for M.B. revealed a pathogenic missense mutation in the DCC gene.

Conclusions: CMM remains an underdiagnosed entity. After evaluation of difficulties with ADLs, adaptation of the school/home environment is recommended.

References: Méneret A, Trouillard O, Depienne C, Roze E. Congenital Mirror Movements. In: GeneReviews® 2015 Mar 12.

« Back to 2017 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/congenital-mirror-movements-when-the-left-hand-doesnt-know-what-the-right-is-doing/