Paroxysmal tonic upgaze in a child with SCN8A-related encephalopathy

Area of Science:

• Genetics
• Neurology
• Pediatrics

Background:

• Pathogenic SCN8A variants cause a spectrum of neurodevelopmental disorders, from infantile seizures to developmental and epileptic encephalopathy.
• An intermediate SCN8A phenotype includes cognitive disability, mild neurological issues, and manageable epilepsy.
• Paroxysmal tonic upgaze (PTU) is a non-epileptic disorder of sustained upward eye deviation, previously seen in other conditions but not SCN8A phenotypes.

Purpose of the Study:

• To report a novel SCN8A deletion associated with an intermediate phenotype.
• To describe the occurrence of paroxysmal tonic upgaze (PTU) in a patient with an SCN8A deletion.
• To add PTU to the spectrum of movement disorders linked to SCN8A gene variants.

Main Methods:

• Clinical case report of a child with a de novo SCN8A deletion.
• Video-electroencephalography (video-EEG) documentation of PTU and seizures.
• Differential diagnosis discussion between PTU and epileptic seizures.

Main Results:

• A child presented with a de novo SCN8A deletion consistent with an intermediate SCN8A-related phenotype.
• The patient exhibited paroxysmal tonic upgaze (PTU), a novel symptom for SCN8A-related disorders.
• Video-EEG confirmed both PTU and epileptic seizures, highlighting diagnostic challenges.

Conclusions:

• This case expands the phenotypic spectrum of SCN8A-related disorders to include paroxysmal tonic upgaze (PTU).
• The findings underscore the importance of considering PTU in the differential diagnosis of SCN8A-related phenotypes.
• This report contributes to understanding the diverse neurological manifestations of SCN8A gene variants.