Palatal myoclonus, eight-and-a-half syndrome, and Holmes tremor in a patient from a single brainstem lesion

Wernekink commissure syndrome with palatal myoclonus at onset: a case report and review of the literature

“…The clinical presentation varies depending on the vascular distribution of midbrain arterial perforators that arise from the tip of the basilar artery, superior cerebellar arteries, and precommunicating P1 segment of posterior cerebral arteries called interpeduncular fossa perforators [ 13 ]. Owing to the proximity of the medial longitudinal fasciculus and trochlear nucleus to the brachium conjunctivum and dentate-rubro-olivary tracts, a caudal midbrain infarction either unilaterally or bilaterally can cause bilateral cerebellar ataxia, dysarthria, multidirectional nystagmus, unilateral or bilateral internuclear ophthalmoplegia, and variable eye movement disorders [ 1 – 10 ]. In contrast to the cases previously reported in the literature (Table 1 ) with palatal myoclonus occurring several months after ischemic stroke, our patient presented with palatal myoclonus from the onset.…”

“…We hypothesize that the cause of early palatal myoclonus in our patient was due to a two-hit mechanism with degeneration of the right olivary nucleus from prior right medullary infarct and acute right caudal midbrain infarct affecting the dentato-rubro-olivary tract on the left side owing to interruption at the decussation, causing bilateral dysfunction and initiating the palatal myoclonus. As described by Bolen et al and Mossuto-Agatiello et al ., despite the degeneration of bilateral olivary nuclei, their patients did not develop palatal myoclonus, thus defining the heterogeneity of this syndrome and its unclear pathophysiology [ 1 , 8 ]. Vascular neurologists should be aware of this unique midbrain lacunar stroke syndrome presenting with an interesting palatal movement disorder, which can be very disabling for the patient.…”

“…Wernekink commissure syndrome is a rare midbrain syndrome characterized by bilateral cerebellar ataxia, internuclear ophthalmoplegia, dysarthria, and delayed-onset palatal myoclonus or Holmes tremor secondary to a stroke in the paramedian caudal midbrain region [ 1 – 4 ]. The midbrain derives most of its blood supply from the posterior cerebral arteries through penetrating perforators from the P1 segment and the basilar artery.…”

“…Depending on the location and extent of infarction in the caudal midbrain, the clinical presentation can be variable. Because the medial midbrain is densely packed with structures such as oculomotor nuclei, descending cerebellar tracts, medial longitudinal fasciculus, and central tegmental tract, a lesion in this area can present with internuclear ophthalmoplegia on the affected side, unilateral or bilateral ataxia, dysarthria, dentatorubral tremor, and delayed-onset palatal myoclonus secondary to hypertrophic degeneration of bilateral inferior olivary nuclei [ 1 – 10 ]. Symptoms are mostly bilateral at presentation, because the paramedian caudal midbrain contains descending cerebellar tracts, central tegmental tract, and other important white matter tracts crossing the midline, making it difficult for the untrained eye to localize the lesion to one vascular territory.…”

Eight and a Half Syndrome from Multiple Sclerosis

“…Other related syndromes included "15 ½ syndrome" (patient with bilateral seventh nerve palsy and one-and-a-half syndrome) and "16 syndrome" (patient with bilateral seventh nerve palsy and hemiparesis and one-and-a-half syndrome) [15]. In an interesting case, a patient's Holmes and palatal tremor and eight-and-a-half syndrome were the results of an injury in the Guillain-Mollaret triangle (composed of the contralateral dentate nucleus, the ipsilateral red and inferior olivary nucleus) [16].…”