Ramsay Hunt syndrome associated with solitary nucleus, spinal trigeminal nucleus and tract, and vestibular nucleus involvement on sequential magnetic resonance imaging

Ramsay Hunt syndrome (RHS) is an acute peripheral facial nerve paralysis typically accompanied by erythematous vesicular lesions of the auricular skin. The etiology is considered to be geniculate ganglionitis due to reactivation of varicella-zoster virus (VZV). Encephalitis is a rare but serious complication of VZV reactivation. Clarifying the regional and temporal evolution of the lesions on magnetic resonance imaging (MRI) would help with understanding the pathology of the lesion, but this information is lacking in encephalitis with RHS. Therefore, here, we reviewed sequential MR images in three RHS cases complicated by brainstem lesions. All the regions of the lesions represent specific neuronal structures—the ipsilateral solitary nucleus (SN) and spinal trigeminal nucleus and tract (STNT) in case 1; bilateral SN, ipsilateral STNT, and vestibular nucleus in case 2; ipsilateral SN and vestibular nucleus in case 3—and this seems to account for the persistent robust symptoms. Case 1 initially showed no abnormalities on MRI and cases 2 and 3 showed weak signals on the first MRI which subsequently plateaued. These observations suggest the timeframe within which it becomes possible to detect regional and temporal evolution, namely, that the distribution of the affected regions expands between weeks 2 and 5 after onset of facial paralysis. These observations and the findings of a literature review indicate that the SN, STNT, and vestibular nucleus are relatively prone to developing encephalitis after RHS.