Generalised Anhidrosis Secondary to Intracranial Haemorrhage.

Dear Editor, A man in his 20s presented with a 3-year history of anhidrosis. There were no autonomic symptoms and he was not on any long-term medications. Five months prior to onset of symptoms, he suffered a ruptured intracranial arteriovenous malformation. On examination, there was spastic right hemiparesis. Sensory and postural blood pressure examinations were normal. Dermatological examination, including hair, nails and teeth, were normal. Thermoregulatory sweat testing was performed in an enclosed room at 32°C and 68% humidity. An admixture of starch and iodine powders was sprayed over his whole body and almost-complete generalised anhidrosis, including the palms, was observed (Fig. 1). Serum thyroid hormones were normal. In vivo high-defi nition optical coherence tomography (HD-OCT)(Skintell®) was performed on multiple sites. Sweat ducts were present and no obstruction of the acrosyringium was visualised (Fig. 2). A cholinomimetic, carbachol (0.1 mL Miostat® 0.01%), was injected intradermally, which stimulated sweat production locally (Fig. 3). Review of brain magnetic resonance imaging (MRI) images revealed haemorrhage in the basal ganglia extending into the third ventricle (Fig. 4). The patient was managed conservatively with advice to avoid strenuous activities and medications that can exacerbate hypohidrosis. Exogenous, drug and dermatological causes of hypohidrosis were excluded through clinical assessment. HD-OCT demonstrated intact sweat ducts and absence of acrosyringium obstruction, thereby excluding ectodermal dysplasia and miliaria respectively. Normal local sweat production upon intradermal injection of a cholinomimetic indicated that the pathology of anhidrosis was neurological rather than dermatological (such as in acquired idiopathic generalised anhidrosis,1 a relatively common cause of generalised anhidrosis). Neurological causes of anhidrosis can result from lesions at the hypothalamus, brainstem, spinal cord or sympathetic chain.2 In our patient, the pathology was most likely at the hypothalamus as lesions at the other anatomical locations need to be bilateral (with resultant extensive neurological defi cits) in order to cause generalised anhidrosis.