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Discussion
Dengue infection is the most common arboviral disease in the tropics and especially in Sri Lanka, where the season usually peaks in June-July each year. Although the clinical spectrum of the disease is well recognized, rare complications of the infection are encountered. Unusual neurological manifestations of the disease such as Encephalopathy and Guillain-Barre syndrome are reported more commonly than others. Diaphragmatic paralysis due to phrenic nerve involvement has only been reported in two previous instances, both from the tropics. Our report introduces the third such patient with this very rare complication.
Our patient had confirmed dengue viral infection which was managed without complications in the ward. He was subsequently found to have a right sided phrenic nerve palsy a month later as confirmed by nerve conduction study and lung function tests. A myopathy or a neuromuscular junction pathology were excluded by normal electromyography. Phrenic nerve compression by mass lesions were excluded by a normal CECT. The presence of f waves on nerve conduction study made Guillain-Barre syndrome an unlikely cause although there was evidence of demyelination.
Post viral phrenic neuropathy has previously been documented following Polio-virus infection (particularly as a post-polio syndrome), Herpes-Zoster infection and Human Immunodeficiency virus infection. The pathophysiology behind the manifestation remains obscure due to paucity of literature but an immune mediated mechanism is suggested. Post viral phrenic neuropathy usually runs a self-limiting course, as was seen in our patient but may run a fulminant course with severe respiratory failure requiring mechanical ventilation.
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