The Guillain–Mollaret triangle in action

Abstract

The Guillain-Mollaret triangle comprises the ipsilateral red nucleus in the midbrain, the inferior olive in the medulla and the contralateral dentate nucleus in the cerebellum: together, these form the dentato-rubro-olivary pathway. Pathology in this triangle disinhibits (and so activates) the inferior olivary nucleus. The olivary nucleus then hypertrophies and its rhythmical discharges may manifest clinically as oculopalatal tremor. We describe three cases with either oculopalatal tremor or MRI evidence of olivary hypertrophy caused by vascular insults to this triangle. It is not clear why only some patients have the oculopalatal tremor. Olivary hypertrophy can be confused with demyelination if the imaging is not put into clinical context. Oculopalatal tremor may occur without olivary hypertrophy since the nucleus atrophies with time. Oculopalatal tremor does not respond to medical treatment. A better understanding of the mechanism of the discharge at a cellular level may lead to more targeted medical treatments.

White matter measures correlate with essential tremor severity—A pilot diffusion tensor imaging study

“…While patients demonstrated changes suggestive of lower myelination levels compared to controls, the opposite correlation between tremor score in patients group suggests a compensatory increase in structural connectivity to balance clinical deficits. Importantly, areas that correlate with objective tremor measures extend to the midbrain, specifically areas around the cerebral peduncles and red nucleus thus including the WM within dentate‐rubro‐olivary pathway (Guillain‐Mollaret triangle), which is considered a tremorgenic loop (Murdoch, Shah, & Jampana, 2016). These findings are consistent with previous studies showing abnormalities in DTI parameters directly within red nucleus (Jia et al., 2011), in retrorubral WM (Shin, Han, Kim, & Lee, 2008) and the Guillain‐Mollaret triangle (Nicoletti et al., 2010) in ET patients.…”

Towards Better Understanding of the Pathogenesis of Neuronal Respiratory Network in Sudden Perinatal Death

“…The G-Mt (Figure 3; Table 1) has three parts: the ipsilateral red nucleus, the inferior olive, and the contralateral dentate nucleus in the midbrain, medulla, and cerebellum to form dentato-rubro-olivary pathway (63). G-Mt is known to be involved in the pathogenetic mechanisms of the palatal myoclonus, in SIDS and SIUDS.…”

Post-stroke dyskinesias

“…Two cerebellar feedback loops are critical for this task, the dentato-rubro-olivary loop and the cortico-cerebellar loop. The dentato-rubro-olivary circuit (Guillain-Mollaret triangle) connects the dentate nucleus in the cerebellum with the contralateral red nucleus and inferior olivary nucleus in the brainstem via the superior cerebellar peduncle, the central tegmental tract, and the inferior cerebellar peduncle, respectively 23. This subcortical circuit is itself part of the larger cerebellar motor network, the cortico-cerebellar circuitry, in which the cerebral and cerebellar cortices are connected together indirectly.…”

“…The motor cortex projects to the cerebellar cortex (via pontine nuclei) which, in turn, projects primarily to the VL nuclei of thalamus and then back to the cerebral cortex (Figure 4). 14,15,23 As the inferior olivary nucleus receives collateral inputs from all afferent pathways projecting to the cerebellar cortex via mossy fibers, it compares intended with executed movements and conveys error signals to the cerebellar cortex via climbing fibers 14,15,24…”

“…It is believed to arise from overactivity of the indirect pathway (and/or underactivity of the direct pathway) leading to an increased pallidal inhibitory output to the thalamus. The resultant thalamic inhibition suppresses the motor cortex and leads to hypokinetic movements 3,23,29…”