INTRODUCTION: Patau syndrome, trisomy 13, is the third commonest autosomal 
trisomy. It is associated with a 25-50% prevalence of epilepsy, but detailed 
electroclinical descriptions are rare. The occurrence of early-onset 
photosensitivity has recently been reported in single patients.
MATERIALS/PATIENTS: We collected electroclinical data on 8 infants (age range 
from 2 months to 3 years and 9 months, median: 17 months) with Patau syndrome 
referred for an EEG in our Clinical Neurophysiology Department between 1991 and 
2011.
METHODS: All EEGs, case-notes, cytogenetic diagnosis and neuroimaging when 
available were reviewed; data on the occurrence of seizures, epileptiform 
discharges, photoparoxysmal response and their characteristics in terms of 
positive frequencies, latencies, grade and duration were noted and analysed.
RESULTS: Two patients had been previously diagnosed with epilepsy (one with 
tonic spasms and one with multiple seizure types). We found 3 patients with 
photosensitive myoclonic epilepsy (37.5%), and one with non-photosensitive 
myoclonic epilepsy. We also recorded non-epileptic myoclonic jerks in one 
patient known to suffer from epileptic spasms. Among photosensitive patients we 
found self-limited, Waltz's grade 2-4, spike-wave/polyspike-wave discharges in 
low, medium and high frequency ranges in two patients and in the high frequency 
range in the third patient, with latencies and duration from less than 1s to a 
maximum of 9s.
CONCLUSIONS: In our cohort of Patau syndrome patients, we found a high 
prevalence of spasms and photic-induced myoclonic jerks. Photosensitivity shows 
an unusual early age of onset.