To characterize the incidence and mechanism behind swelling in those with Dravet syndrome (DS), which to date remains undescribed in medical literature.

Dravet syndrome is a developmental epileptic encephalopathy in which children are born otherwise normal, however as seizures begin these patients develop neurocognitive delay, and by adolescence develop a crouched gait and occasional limb swelling. Without previously published information on limb swelling in DS, a thorough description and investigation into the incidence and mechanism is indicated.

An IRB-approved survey was posted to the national DS Foundation support group's Facebook page and emails were sent from their listserv from 08/18/2023 to 09/21/2023. In this parent-directed survey, information regarding their child’s demographics, gait, medications, and the presence of limb edema was examined and analyzed.

Of the 265 surveys completed, 44 (17%) reported past or current limb swelling. Of those that reported swelling, 35 (80%) were in the feet or ankles, 20 (39%) in the legs, knees, or thighs, 11 (25%) in the hands, 6 (14%) elsewhere in the upper extremity, and 9 (20%) in the face. Interestingly, 91% of areas reported were bilaterally involved. Mean age of swelling onset was 12.4 years (median 12y).

Limb swelling was reported in 35% of those >16 years old, 13% of those 7-16 years old, and 3% of those <7 years old. Though 69% reported abnormal gait, 95% of those with swelling reported abnormal gait, and 25% reported painful swelling. An association was found between taking valproic acid or clobazam and onset of swelling.

Limb edema may occur in those with DS, and most commonly presents in the lower extremity, bilaterally, after the age of 12y, and concurrent with gait disturbance. Though the exact incidence and mechanism of limb swelling remain unclear, this may be a consequence of progressive mechanical musculoskeletal dysfunction and/or medication effect.