Tapping-lips aggravated interictal bilateral discharges in EEG in the patients with Rett syndrome: a case report

Abstract

Background Rett syndrome (RTT) is a severe neurodevelopmental disorder mainly affecting females. One of the main clinical manifestations is hand stereotypies, which is presumed to based on dysfunction rather than on structural impairment. Reflex interictal discharge precipitated by tapping-lips in electroencephalogram (EEG) is a rare phenomenon among RTT. Case presentation We firstly reported a case of RTT concerning interictal reflex discharge precipitated by tapping- lips. The child, female, 5 years old, presented with a significant regression in motor development and language skills. She almost always tapped the lips with the right hand and stopped only when was interrupted. Her EEG results displayed extensive low amplitude fast wave could be elicited by lightly and slowly- rhythm tapping lips and multifocal bilateral discharges could be precipitated by relatively stronger and quicker rhythm action. It was when the movement stopped that corresponding discharges immediately disappeared. Besides, the reflex discharges were not precipitated by tapping- lips using observer’s hand at the certain tempo and intensity. The hand stereotypies did not respond to antiepileptic drugs. Conclusions Tapping- lips may be a somatosensory stimulation to precipitate interictal discharges in RTT, which may provide another idea to enrich the insight on hand stereotypies of RTT.

Reviewing Evidence for the Relationship of EEG Abnormalities and RTT Phenotype Paralleled by Insights from Animal Studies

“…CTS can be suggested to reflect altered excitability of the perisylvian cortical areas that may contribute to motor and speech disturbances in RTT patients. Evidence for the relevance of CTS to motor control comes from studies that found a suppression of focal CTS by hand tapping/clapping in a subgroup of patients with RTT with six representative cases described in the literature [ 60 , 61 , 75 , 93 ]. In line with these observations, Cooper and colleagues reported a decrease in EEG abnormality during hyperventilation that is accompanied by increased movement in young girls with RTT [ 74 ].…”

“…Noteworthy, in some cases CTS can be precipitated by specific movements. In a case reported by Luo and colleagues, CTS were only induced by right hand-to-lips tapping but not by right hand tapping cheek or abdomen, the left hand tapping lips or observer’s hand tapping the lips [ 60 ]. Roche Martínez and colleagues reported three epileptic Rett patients with reflex seizures triggered by food intake or proprioception [ 66 ].…”