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Palatal Tremor with Progressive Ataxia Secondary to A Dural Arteriovenous Fistula

A 71-year-old man presented with a six-month history of progressive dysarthria, dysphagia, and unspecific dizziness. Clinical examination revealed a 2-3-Hz tremor involving palatal, laryngeal, pharyngeal, and facial muscles, as well as gait ataxia (Supporting Video 1). Seventeen months prior, a dural arteriovenous fistula (DAVF; Cognard type 3) causing edema in the cerebellum and brainstem (Fig. 1B) had been successfully treated. The initial symptoms leading to the diagnosis of the fistula had consisted of severe ataxia (inability to walk), dysarthria (speech nearly incomprehensible), and disorders of the ocular motor system (saccadic pursuit, gaze-evoked nystagmus) as well as vertigo. These clinical findings had been posture-dependent and had markedly worsened in an upright position. After successful hybrid treatment of the fistula, all symptoms had significantly improved. MRI after tremor onset showed bilateral T2-hyperintensity of the inferior olivary nucleus (ION; Fig. 1E). Moreover, retrospective analysis of multiple MRI before and after DAVF-treatment demonstrated progressive cerebellar and brainstem atrophy (Fig. 1A-E). This analysis suggests a secondary degenerative process that may have been caused by venous hypertension and subsequent vasogenic edema as initial injury within the dentato-rubroolivary pathway, formerly referred to as the Guillain–Mollaret triangle. Lesions involving this pathway, but sparing the olives, are known to cause denervation and degeneration of the ION and manifest as a tremor of branchial-derived muscles. The underlying hypertrophic olivary degeneration (HOD) develops the most several weeks or months after denervation, which correlates with the delayed onset of the symptoms. Moreover, contralateral atrophy of the cerebellar cortex and dentate nucleus may occur in association with HOD. This is consistent with the observation of delayed and progressive cerebellar ataxia in some patients with oculopalatal tremor in particular after larger acute brainstem lesions. In conclusion, we present a case of a, most likely, symptomatic palatal tremor (SPT) secondary to a DAVF. The combination of progressive gait ataxia, palatal tremor, and olivary degeneration could also be classified as progressive ataxia and palatal tremor (PAPT) syndrome, which is considered to be a subtype of SPT. However, while SPT occurs secondary to an identifiable monophasic structural lesion of the brainstem or cerebellum, PAPT is a sporadic or familial disorder of a yet undetermined, presumed degenerative, etiology with progressive cerebellar atrophy, and in most cases HOD. Recently, PAPT has been referred to as a novel tauopathy. The rare cases of palatal tremor in combination with tardive progressive ataxia after rather large brainstem lesions could be equally classified as sporadic PAPT syndromes with identifiable structural lesion as a specific subtype of SPT. This classification might also be applicable in the case presented here. We hypothesize that the extended venous stasis due to the DAVF led to a bilateral injury of the projections of the dentato-rubro-olivary pathway and subsequently to bilateral olivary degeneration with cerebellar atrophy. Finally, it is important to note that SPT and PAPT have to be distinguished from essential palatal tremor for which there is no evidence for structural lesions and HOD.