ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2006) 12 P31

Severe hyponatremia and subsequent extra-pontine myelinolysis as a presentation of addison’s disease

C Strey, M Gurnell, K Chatterjee, D Woods & H Simpson

Addenbrooke’s Hospital, Cambridge, United Kingdom.

A 39 yr-old female with a past medical history of a non-metastatic ductal breast carcinoma, presented to hospital with a two-week history of vomiting and dizziness. Clinical examination was essentially normal apart from pigmentation of her mastectomy scar, palmar creases and buccal mucosa. Investigations revealed a plasma sodium (Na) 102 mmol/l, potassium 4.9 mmol/l, plasma osmolality 219 mOsm/kg, urine osmolality 173 mOsm/kg and urine Na 36 mmol/kg. She was treated with fluid restriction (700 ml/day), demeclocycline and intravenous Na chloride (1 l /24 h). Plasma Na increased to 123 mmol/l over three days (maximum rate of 11 mmol/24 h). A synacthen test was abnormal (cortisol 254 nmo/l pre, 243 nmol/l 30 min post ACTH). Over the next few days she deteriorated, developing slurred speech and unsteady gait. Neurological examination revealed slow speech, a gait with reduced arm swing and stride length, marked bradykinesia and rigidity. MRI brain was normal. She was commenced on iv hydrocortisone. Despite normalisation of her plasma Na her condition deteriorated rapidly and on day 6 she was transferred to the ICU of a tertiary centre requiring intubation and ventilation. At this point she had developed severe rigidity and a jerky, resting tremor. Differential diagnoses of a paraneoplastic syndrome or leptomeningeal carcinomatosis were considered. She was treated with antiparkinsonian medication and plasmaphoresis. Repeat synacthen test was abnormal, with an ACTH of 432 ng/l, and anti-adrenal antibodies were positive and fludrocortisone was commenced. A second MRI head at day 7 was normal, as were all investigations suggestive of metastatic carcinoma. A third MRI head at day 18 showed high signal in the lentiform and caudate nuclei consistent with extra-pontine myelinolysis. She was discharged from hospital after five months and has made a slow but almost complete recovery.

Acute neurological presentations in the context of Addison’s disease are rare posing a diagnostic challenge. This patient presented with an extremely low plasma sodium, the treatment of which resulted in severe extra-pyramidal symptoms due to extra-pontine myelinolysis.

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