Neuromyelitis Optica (NMO) is a neuro-inflammatory condition usually presenting with optic nerve and spinal cord events, caused by autoimmunity to Aquaporin 4 (AQ4) channels in the central nervous system (CNS). The high density of AQ4 channels in the hypothalamus and area postrema mean that NMO can occasionally present with atypical features. We present a 56-year old South Asian man, who presented with hiccoughs and Syndrome of inappropriate antidiuretic hormone (SIADH ) and was eventually diagnosed with NMO.
Clinical Case: Patient presented with 3-day history of intractable hiccoughs; physical examination including neurological, was unremarkable. On admission, serum sodium was 123 mmol/l (135–145 mmol/l), urine sodium 61 mmol/l, urine osmolality 551 mosm/kg. Thyroid function tests, cholesterol and cortisol levels were within the normal range, suggesting SIADH. The CT Head was unremarkable; CT CAP demonstrated no evidence of malignancy. In the intensive care unit, hypertonic saline was administered, and he was fluid restricted. The serum sodium normalised, and he was discharged. He re-presented 2 weeks later with tingling and numbness to the left hand. He subsequently developed weakness in both upper limbs and dyspnoea. This time serum sodium was 137 mmol/l. CSF was acellular with normal protein and glucose with absent oligoclonal bands. Paraneoplastic serology was negative, however Aquaporin4 antibodies (AQ4Abs) were present. MRI Brain demonstrated a small focus of enhancement at the lateral aspect of the right ventricle and MRI Spine demonstrated a cervical cord lesion extending from the lower medulla to C7, with contrast enhancement suggestive of transverse myelitis. 18FDG PET imaging was normal. Intravenous methylprednisolone and plasma exchange were administered. He was started on mycophenolate mofetil and the prednisolone tapered. He improved clinically and follow-up scans demonstrated resolution of the cervico-medullary enhancement and reduction of the cord swelling.
Discussion: SIADH in NMO is attributed to targeting of the hypothalamic AQ4 channels by AQ4Abs. The intractable hiccoughs are associated with inflammatory involvement of the area postrema. The combination of SIADH and intractable hiccoughs is rare, however both regions contain relatively high levels of aquaporin 4 channels and the combination should make clinicians strongly consider NMO even in the absence of the classical neurological symptoms.
05 Sep 2020 - 09 Sep 2020