DISCUSSION
The opercular syndrome(OS) includes bilateral corticobulbar involvement with voluntary facio-labio-pharyngo-glosso-laryngo-brachial paralysis with well-preserved automatic and reflex movements.(8) It is a sequalae of bilateral lesions of the anterior opercular area surrounding the insula formed from gyri of the frontal, temporal and parietal lobes. It is a form of cortical type of pseudobulbar palsy.(8)
The etiology encompasses vascular lesions including thrombotic or embolic multiple strokes, particularly in adults; infections of the nervous system, for example herpes simplex encephalitis, and toxoplasmosis secondary to AIDS; acute disseminated encephalomyelitis; head trauma; vasculitis; multiple sclerosis; perinatal difficulties; and perisylvian cortical dysplasias.(1)(8)
OS is commonly associated with infectious cause in childhood (72.7) including herpes simplex virus. The virus is the most prevalent cause (37.5%). Likewise in adults OS is more commonly linked to cerebral infarction.(53.3%)(9) with viral cause being less common. We found only one previous case related to OS with EBV infection. EBV encephalitis causes damage to the deep nuclei of the basal ganglia and thalamus, which is different from our findings. Our patient’s PCR results showed no amplification of EBV DNA. Only 75% of patients with a positive EBV serological test show detectable EBV DNA. The remaining 25% can have negative PCR results.(9)
The operculum includes the area covering the island of Reil, and is made up of parts of the frontal, parietal, and temporal cortex and lesions which disrupts the connections between these areas and the relevant cranial nerve nuclei in the brainstem can cause the suprabulbar palsy of the opercular syndrome. This explains the preservation of emotional and automatic bulbar reflex movements, which relies on the use other neural pathways.(10)
In contrast to pseudobulbar palsy, the opercular syndrome is characterized by lack of sphincter disturbances, the rarity of pathological laughing, the decreased tone of the affected muscles, and the abolished gag reflex and it differs from bulbar palsy in the lack of fasciculation, atrophy and denervation, and in the preservation of involuntary innervation and of reflexes except for the gag reflex.(10) The patient had mild residual dysarthria as seen in other studies. Incomplete resolution of neurologic symptoms is consistent with prior reports of HSV-induced FCMS.(15)
Weller et al classified opercular syndrome based on etiology; i.e. (a) Classical form most often related to vascular etiology; (b) Subacute form due to central nervous system infections; (c) Developmental form most often related to neuronal migration disorders; (d) Reversible form in children with epilepsy; and (e) Rare type related with neurodegenerative disorders.(11)
Patient can present with opercular syndrome in the setting of initial near normal cerebrospinal fluid (CSF) studies as seen in the early phase of our case. HSV encephalitis should be suspected and treated in febrile patients with otherwise unexplained neurologic deficits even if initial CSF analysis is unremarkable.(12)
The clinical manifestation is fairly uncommon, however radiological evidence of involvement of the operculum in HSE is commonly evident. MRI is very sensitive in showing opercular damage, depending on the etiology.(13)
The limbic system is usually affected by HSVE; the most commonly affected areas are the medial temporal lobes, but it can also impact the insular, cingulate, and fronto-basal cortex. The lesions are unilateral or bilateral. On a brain MRI, regions of T2 and FLAIR hyperintensities involving the cortex and white matter are commonly observed. Although a few cases of basal ganglia involvement have been recorded in HSVE, basal ganglia are typically avoided.(13)(14)
In terms of prognosis for HSE, it is critical to begin antiviral therapy at an effective dose and time duration timely along with supportive care. Inadequate dosing and treatment can lead to a poor prognosis. Many authors believe that 21 days would be secure. Acyclovir and valacyclovir are suggested as prophylaxis against HSE. We treated our case with intravenous acyclovir for three weeks and continued for one more week until the control CSF PCR findings came back negative. It is favorable for prognosis to continue the intravenous treatment for at least four weeks, even if the control CSF HSV-1 PCR goes negative.(2)