Unilateral negative myoclonus caused by herpes simplex virus encephalitis

Area of Science:

• Neurology
• Infectious Diseases
• Neuroimmunology

Background:

• Herpes simplex virus (HSV) encephalitis is a severe brain infection.
• Neurologic complications of HSV encephalitis include various movement disorders like chorea and myoclonus.
• Negative myoclonus (NM) has not been previously associated with HSV encephalitis.

Purpose of the Study:

• To report the first documented case of negative myoclonus (NM) in a patient with herpes simplex virus (HSV) encephalitis.
• To characterize the clinical and electrophysiological features of NM in this context.

Main Methods:

• Case report of a patient diagnosed with HSV encephalitis.
• Clinical assessment of movement disorders.
• Polygraphic monitoring including electroencephalography (EMG) to analyze muscle activity during NM episodes.

Main Results:

• The patient presented with unilateral arm and leg negative myoclonus.
• Polygraphic monitoring revealed electroencephalography (EMG) silent periods ranging from 50 to 250 ms.
• No detectable EMG correlate was found during the NM episodes.

Conclusions:

• This case expands the spectrum of neurologic manifestations of HSV encephalitis.
• Negative myoclonus is a potential, previously unreported, complication of HSV encephalitis.
• Further research is needed to understand the pathophysiology of NM in HSV encephalitis.