Objective: Description of two pediatric cases with refractory dystonic storm secondary to GNAO1 (G- Protein Subunit Alpha O1) mutation treated with pallidal deep brain stimulation (DBS).

Background: Mutations in the GNAO1 gene produce heterogeneous syndromes combining epileptic encephalopathy and hyperkinetic movement disorders. These patients can present exacerbations of the hyperkinetic disorder, including dystonic storm, a life-threatening complication.

Method: We present two cases with previous psychomotor delay and hyperkinetic disorder consisting in choreoathetosic movements and dystonic postures, and epilepsy in the case of the female patient.
– 14 years-old-male with a heterozygous mutation in the GNAO1 gene (c.709G>A (p.Glu237Lys)). In the context of hip osteotomy surgery, he presented a dystonic storm.
– 6 years-old-female with a heterozygous mutation in GNAO1 gene (c.607 G>A (p.Gly203Arg)). She presented a dystonic storm triggered by a respiratory syncytial virus infection.

Both were admitted in the Pediatric Intensive Care Unit and treated with clonidine, chloral hydrate, diazepam, midazolam, and topiramate, lacosamide and propofol in the case of the female patient. With partial control of the dystonic storm, deep brain stimulation was decided in both cases. Under general anaesthesia, bilateral electrodes (Medtronic® 3389) were inserted into the bilateral internal globus pallidus (GPi) and connected to an implantable neural stimulator (Medtronic® ACTIVA RC) in their abdomen. Post-surgery cranial MRI was performed showing no complication and a correct placement of the electrodes.

Results: Resolution of the dystonic storm was achieved in 3 and 15 days respectively, with good outcome of the hyperkinetic disorder. Final stimulation settings were as follows:
– 14 years-old-male patient: left GPi case+, contact 0–, 90 microseconds, 130 Hz, 2.6 V and right GPi case+, contact 8–, 90 microseconds, 130 Hz, 2.6 V.
– 6 years-old-female patient: left GPi  case+, contact 0–, 90 microseconds, 130 Hz, 3.1V and right GPi contact 8–, contact 9+, 90 microseconds, 130 Hz, 3.1V

Conclusion: Dystonic storm is a life-threatening complication that could be managed with DBS in refractory cases. These two patients with GNAO1 mutation, treated successfully with pallidal DBS, can be added to the few cases reported in the literature with this mutation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/pallidal-deep-brain-stimulation-in-gnao1-mutation-dystonic-storm-a-description-of-two-pediatric-cases/