Bilateral mirror writing movements (mirror dystonia) in a patient with writer's cramp: Functional correlates

Abstract

A recent prospective analysis on writer's cramp showed that up to 44.6% of patients in a series of 65 presented mirror dystonia, defined as involuntary movements of the resting hand, abnormal posture, tremor, and jerks occurring while writing with the opposite hand. A clinical case is presented, with videotape evidence of right-handed writer's cramp, with mirror movements elicited while writing using either hand. Functional magnetic resonance imaging studies are compared both to those of a normal patient and to those from a patient with writer's cramp but lacking mirror dystonia. Widespread bilateral activation of cortical motor areas contralateral to the mirror movements in patients with writer's cramp and mirror movements suggests, that bilateral activation of the primary motor cortex may account for the appearance of these mirror movements. Further studies need to be conducted to determine whether mirror movements in dystonic patients appear as a result of loss of intra- and/or interhemispheric cortical inhibition or are simply a consequence of the sustained effort these patients need to exert while writing using a dystonic hand.

Focal hand dystonia, mirror dystonia and motor overflow

“…While a failure of surround inhibition might explain the ipsilateral overflow in our FHD patients, contralateral overflow movements may be due to either transcallosal inhibitory failure leading to activation of the motor areas ipsilateral to the movement, activation of uncrossed corticospinal fibres, or both [9]. This is supported by functional MRI studies in patients contralateral or mirror dystonia [10].…”

Continuous involuntary hand movements and schizencephaly: epilepsia partialis continua or dystonia?

“…This could account for the bilateral brain activation that was observed during fMRI. Such bilateral activation pattern has been also found in patients with writer cramp and mirror movements [10] and probably reflects impaired transcallosal inhibition from the right affected to the left unaffected cortex, while the activation of ipsilateral motor pathways is more unlikely since the cortical activation while moving the unaffected hand was strictly contralateral.…”

Mirror movement associated with neural tube defects

“…The hypothesis related to spinal origin for mirror movements varied from activity in the ipsilateral corticospinal tract (Mayston et al1997) to defi ciency in the pyramidal decussation causing development of alternative, less specifi c pathways (Krams et al 1999), abnormal ipsilateral and bilateral fast conducting corticospinal projections with abnormal common presynaptic input (Farmer et al 1990;Farmer 2005;Marcelo et al 2006), and a loss of inhibition of contralateral crossed projections, rather than from a loss of inhibition of the ipsilateral uncrossed pathway (Nass 1985;Aranyi and Rosler 2002;Marcelo et al 2006).…”