Child In Stupor, No Fever Or Vomiting, Has Auditory Hallucination And Memory Loss, MRI Normal, History Of Head Trauma

9 years old male pt , came to paediatrics ER , stuper condition , no fever or vomiting or headach has bowel and urinery incontinence since 1 week has myoclonus since 3 months has auditory hallucination and loss memory since 3 months past history : one attack of seizure before 8 month there is history of head trauma since 2 years the first syptom was before 9 month was speech disorder then after 2 weeks pt develop gait ataxia . MRI normal LFT and RFT normal CBC and serum electrolyte normal chest x ray normal doctors in my poor country cannot reach diagnosis please help in examination : reactive dilated pupil pt is aphasic Bp 90 on 60 afebrile no jaundice no pallor no cyanosis there is visual field defect positive plantar reflex bilateral knee reflexes are abscence in both no neck rigidity , negative kerng sign