A rare syndrome, Dyke-Davidoff-Masson Syndrome (DDMS), with a diagnostic 
conundrum, and the way it was solved is presented. A 13-year-old boy presented 
with recurrent seizures for the past 10 years. He had been treated with 
anticonvulsant medication which was satisfactory at first but later the seizures 
recurred. Recently, the frequency of the seizures increased with preictal 
dizziness and postictal drowsiness. Physical examination revealed mild left 
hemiparesis and left deviated gait irregularity. He was mentally alert but had 
not achieved all the developmental milestones as compared to normal child of his 
age. CT and MRI scan of the head showed hemiatrophic cerebral parenchyma with 
prominent sulci and encephalomalacia. 24-hour intensive video EEG monitoring 
revealed suppression of alpha rhythm and local slow wave activity on the side of 
the atrophic hemisphere. PET-CT showed highly functional left cerebral 
hemisphere and less functional right cerebral hemisphere. The patient underwent 
functional hemispherectomy under neurophysiological monitoring and the 
nonfunctional brain tissues were resected while selectively preserving the 
functional areas detected by fMRI and PET-CT scan. During follow up, the patient 
was seizure free as well as without difficulties in performing his daily 
activities and communications. Functional hemispherectomy for DDMS patient has a 
good prognosis.