Reply: Congenital mirror movements: lack of decussation of pyramids Mirror movement: from physiopathology to treatment perspectives

Sir,Patients with congenital mirror movements have structural abnormalities of the corticospinal and transcallosal pathways, and functional deficits of interhemispheric inhibition and motor planning processes, which lead to the inability to perform independent hand movements (Gallea et al. , 2013). In their Letter to the Editor, Brandao et al. (2014) suggest that (i) the abnormal pyramidal decussation could be a biomarker to diagnose congenital mirror movements; and (ii) neuromodulation by way of artificial stimulation could be used as therapeutic means to influence interhemispheric inhibition and/or motor planning processes.Congenital mirror movements is a developmental movement disorder and syndromic diagnosis is easily made, based on clinical examination (Bonnet et al. , 2010), making the neuroimaging or neurophysiological evidence of abnormal pyramidal decussation rather obsolete for this purpose. Linking abnormal pyramidal decussation to a genetic cause of isolated congenital mirror movement has not been properly investigated to date. Comparison of the pyramidal tract morphology between patients with DCC mutation/deletion, RAD51 mutation/deletion and no mutation/deletion in DCC or RAD51 has not been investigated. Using transcranial magnetic stimulation (TMS) in a DCC-MM patient, it was demonstrated that each M1 cortex was abnormally connected to both sides of the spinal cord via separate crossed and uncrossed fast conducting corticospinal projections (Cincotta et al. , 2003; Depienne et al. , 2011). It is thus likely …