Pre- and postsurgical cognitive trajectories and quantitative MRI changes in Rasmussen syndrome

To quantify the longitudinal cognitive trajectory, before and after surgery, of Rasmussen syndrome (RS), a rare disease characterized by focal epilepsy and progressive atrophy of one cerebral hemisphere.

Thirty-two patients (mean age = 6.7 years; 17 male, 16 left hemispheres affected) were identified from hospital records. The changes in intelligence scores during 2 important phases in the patients' journey to treatment were investigated: (1) during the preoperative period (n = 28, mean follow-up 3.4 years) and (2) from before to after surgery (n = 21 patients, mean time to follow-up 1.5 years). A volumetric magnetic resonance imaging (MRI) analysis of longitudinal changes in gray matter volume was conducted in a subsample of 18 patients.

(1) IQ during the preoperative period: At baseline assessment (on average 2.4 years after seizure onset), the left RS group had lower verbal than nonverbal intellectual abilities, whereas the right group exhibited more difficulties in nonverbal than verbal intellect. Verbal and nonverbal scores declined during the follow-up in both groups, irrespective of the affected side. Hemispheric gray matter volumes declined over time in both groups in affected as well as unaffected hemispheres. (2) Postoperative IQ change: The left surgery group declined further in verbal and nonverbal intellect. The right group's nonverbal intellect declined after surgery, whereas verbal abilities did not. Patients with higher abilities preoperatively experienced large declines, whereas those with poorer abilities showed little change. Postoperative seizures negatively impacted on cognitive abilities.

During the chronic phase of the disease, parallel decline of verbal and nonverbal abilities suggest progressive bilateral hemispheric involvement, supported by evidence from MRI morphometry. Postsurgical cognitive losses are predicted by greater presurgical ability and continuing seizures. A shorter duration from seizure onset to surgery could reduce the postoperative cognitive burden by minimizing the decline in functions supported by the unaffected hemisphere.