Autoimmune encephalitis: SAQ

This girl presents the classic, multidomain picture of anti-NMDA receptor encephalitis: a subacute psychiatric phase of agitation and hallucinations, followed by seizures, orofacial dyskinesia, and hypoventilation, with a normal MRI and a lymphocytic inflammatory CSF with oligoclonal bands. The antibody result is pending and must not delay treatment, because early immunotherapy is the strongest predictor of good outcome. [1]

Question 1 (10 marks)

Outline your immediate assessment, the investigations you would request, and your initial management over the first 24 hours. [1]

On recognition I would treat this as probable anti-NMDA receptor encephalitis and admit her to a monitored bed given the hypoventilation and obtundation. My first priority is the airway and breathing, because hypoventilation is a defining and life-threatening feature: I would secure the airway, monitor oxygen saturation and respiratory rate, and prepare for ventilatory support, and place her on cardiac and haemodynamic monitoring for the autonomic instability with tachycardia and blood pressure swings. [5]

I would treat ongoing seizures with a benzodiazepine ladder and set up continuous EEG, because non-convulsive status is common and easy to miss behind an obtunded patient. The workup runs in parallel: I would send the CSF for cell count, protein, glucose, oligoclonal bands, and viral polymerase chain reaction including herpes simplex virus; draw a paired CSF and serum neural antibody panel with CSF as the more sensitive sample for NMDAR; and obtain an EEG for the extreme delta brush pattern and background slowing. The MRI is already normal, which is fully compatible with the diagnosis. [1]

I would start empirical intravenous aciclovir and antibiotics until infection is excluded, and I would search for an ovarian teratoma with pelvic ultrasound then pelvic MRI in this post-pubertal girl. I would start first-line immunotherapy as soon as infection is reasonably excluded and without waiting for the antibody result, giving intravenous methylprednisolone 20 to 30 mg per kg per day, maximum 1 g, for three to five days, combined with intravenous immunoglobulin 2 g per kg over two to five days. I would involve paediatric neurology and intensive care and plan retrieval to a tertiary centre. [7]

Question 2 (10 marks)

She has a poor response to first-line therapy at day 12 and a left ovarian teratoma is confirmed on pelvic MRI. Discuss your second-line management, the rationale for early escalation, and the prognosis and follow-up plan you would discuss with the family. [2]

A poor response at 10 to 14 days is the trigger to start second-line immunotherapy, because the Titulaer cohort showed that early immunotherapy and early second-line therapy within the first four weeks are independent predictors of good outcome. My second-line regimen is rituximab 375 mg per m2 weekly for four weeks, and or cyclophosphamide 750 mg per m2 monthly, per the international paediatric consensus. I would arrange urgent gynaecological removal of the ovarian teratoma, because tumour removal is the single most effective intervention in paraneoplastic anti-NMDAR disease and can transform the course. [2][7]

I would quote the family the prognosis that good outcome is achieved in around seventy-five percent within the first twenty-four months, with relapse in around twelve to fifteen percent, so surveillance continues after discharge. I would be honest that recovery is prolonged, that cognitive impairment, psychiatric sequelae, residual epilepsy, and movement disorder can outlast the acute illness by months, and that formal neuropsychological assessment and a structured school reintegration plan are part of treatment rather than an afterthought. I would give the family a relapse safety-net, noting that relapse may follow a premature taper of immunotherapy, and arrange paediatric neurology follow-up with cognitive and psychiatric assessment. [6]

I would also counsel that around twenty percent of children who recover from herpes simplex encephalitis develop a secondary autoimmune encephalitis, so any new neurological relapse after prior HSE is treated as possible post-HSE autoimmune disease rather than recurrent infection. [11]