MRI and neurological presentation of hypertrophic olivary degeneration

Palatal tremor: a literature review and case report

PURPOSE

Palatal tremor is a rare involuntary rhythmic oscillation of the soft palate which may be found in isolation or in association with other forms of segmental myoclonus. It is seldom reported in the literature and varies considerably in its aetiology, clinical presentation and management.

METHODS

The Google Scholar database was searched to retrieve relevant research articles. We also outline a case of essential palatal tremor in a 17-year-old male.

RESULTS

Symptomatic palatal tremor is due to established pathophysiology whereas essential palatal tremor is idiopathic in origin. We discuss the current assessment and management (surgical and non-surgical) of both essential and symptomatic palatal tremor.

CONCLUSION

There is currently no single treatment considered curative for either type of palatal tremor. Further research into and discussion of this rare condition amongst clinicians would be beneficial.

Radiological Hypertrophic Olivary Degeneration Following Posterior Fossa Tumor Surgery

BACKGROUND

Hypertrophic olivary degeneration (HOD) is a rare form of transsynaptic degeneration, caused by injury to the dentato-rubro-olivary pathway (DROP). Radiologically, this manifests as T2 hyperintensity, with or without enlargement of the inferior olivary nucleus. The purpose of the study was to evaluate the incidence, associated imaging characteristics, potential etiologies, latency period, and temporal progression of HOD in patients undergoing surgical resection of posterior fossa tumors (PFTs).

METHODS

A retrospective analysis of patients with PFTs and postsurgical magnetic resonance imaging scans was conducted. HOD was diagnosed based on inferior olivary nucleus signal abnormalities and size changes. Demographics, tumor characteristics, time to HOD onset, involved DROP components, and clinical symptoms were recorded.

RESULTS

HOD was seen in 40 (6.2%) patients following PFT surgery. Twenty six patients were aged 17 years or less, while the rest were aged more than 17 years. Medulloblastoma was the most frequently diagnosed tumor type (n = 25), followed by pilocytic astrocytoma (n = 8), ependymoma (n = 6), and high-grade glioma (n = 1). No statistical association was found between the development of HOD and tumor grade (P = 0.882). Ataxia was the most commonly reported clinical symptom (n = 15). The time elapsed between surgery and the diagnosis of HOD varied, with median intervals of 1 month, 5 months, and 37 months for different stages. Dentate nucleus was the most commonly affected component of the DROP (n = 36).

CONCLUSIONS

HOD is a frequently overlooked postoperative complication following PFT resection. Increased recognition of HOD by neuroradiologists is essential for timely diagnosis and avoidance of unnecessary diagnostic procedures.

Hypertrophic olivary degeneration secondary to a Guillain Mollaret triangle cavernoma: Two case report

Hypertrophic olivary degeneration (HOD) is a rare form of transsynaptic degeneration. It is caused by a damage at the Guillain-Mollaret triangle (GMT), which is defined by three anatomical structures: the dentate nucleus, the red nucleus, and the inferior olivary nucleus (ION). Clinically, it may be revealed by palatal myoclonus. On MRI, it appears as a unilateral or bilateral enlargement of the inferior olivary nucleus which shows a high signal intensity on T2-weighted images, with sometimes a cerebellar atrophy. Here we report 2 cases of healthy patients which present hemorrhagic brainstem cavernomas, complicated later by the development of palatal myoclonus and cerebellar ataxia, with MRI features corresponding to an (HOD) secondary to a (GMT) cavernoma. The purpose is to explain the mechanism of (HOD) subsequent to lesion in (GMT), and to describe magnetic resonance imaging features.

A Rare Presentation of Idiopathic Unilateral Hypertrophic Olivary Degeneration

Hypertrophic olivary degeneration (HOD) is a rare form of trans-synaptic degeneration affecting the inferior olivary nucleus (ION). Its classical description involves a lesion in the Guillain-Mollaret triangle (GMT), characteristic imaging findings, and associated oculopalatal tremor. However, understanding of this disease entity is incomplete, as its overall rarity has limited strong classification. Case reports and small studies indicate that a variety of presentations can occur, including non-existent or non-classical lesions as well as variations in physical symptoms. Here we report the exceedingly rare case of idiopathic, nonlesional, unilateral HOD in a female patient.

The Guillain-Mollaret triangle: a key player in motor coordination and control with implications for neurological disorders

The dentato-rubro-olivary pathway, also known as the Guillain-Mollaret triangle (GMT) or myoclonic triangle, consists of the dentate nucleus, the red nucleus, and the inferior olivary nucleus (ION). GMT is important for motor coordination and control, and abnormalities in this network can lead to various neurological disorders. The present study followed a systematic approach in conducting a review on GMT studies. The inclusion criteria were limited to human subjects with primary objectives of characterizing and evaluating GMT syndromes, and the methodology used was not a determining factor for eligibility. The search strategy used MeSH terms and keywords relevant to the study's objective in various databases until August 2022. A total of 76 studies were included in the review after assessing 527 articles for eligibility based on the final inclusion criteria. Most of the studies evaluated the GMT in human subjects, with the majority utilizing magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), or combination of them. The review found that Hypertrophic olivary degeneration (HOD), a common consequence of GMT damage, has diverse underlying causes, including stroke, brainstem cavernous malformations, and structural impairments. Palatal tremor, ocular myoclonus, ataxia, nystagmus, and vertigo were frequently reported symptoms associated with HOD. This systematic review provides comprehensive insights into the association between GMT and various neurological syndromes, shedding light on the diagnostic, etiological, and prognostic aspects of GMT dysfunction. Understanding the role of the GMT and its implications in movement disorders could pave the way for improved treatment options and better management of neurological conditions related to this critical brainstem pathway.

Clinical and Imaging Profile of Patients with Palatal Tremor

Background

Palatal tremor (PT) is an uncommon movement disorder that may be classified into symptomatic (SPT) or essential (EPT). The etiology of SPT is varied, with involvement of the Guillain-Mollaret triangle (GMT) and inferior olivary hypertrophy. EPT is associated with ear clicks and normal imaging and may have a functional basis.

Objectives

This study aims to explore the clinical and radiological features of a large cohort of patients with PT.

Methods

This is a retrospective chart review of patients with PT who were evaluated by the movement disorders subspeciality of the neurology department. Demographic, clinical, and imaging details of patients with PT were documented.

Results

A total of 22 patients with PT comprising 17 with SPT and 5 with EPT were included in this study. No patient was aware of the PT. Ear clicks were reported in 2 patients with SPT and in 3 patients with EPT. The most common etiology for SPT was vascular, followed by degenerative conditions. Patients with SPT had associated features such as tremor (70.6%), ataxia (64.7%), dystonia (52.9%), myoclonus (17.6%), and eye movement abnormalities (75%). Lesions involving the GMT were found in 82% of patients with SPT. Apart from PT, patients with EPT had no other motor symptoms, and imaging was normal. Of the patients with EPT, 2 had additional functional movement disorders.

Conclusion

PT has significant etiological heterogeneity and can be easily missed because of the lack of awareness by patients. Involvement of the inferior olivary nucleus may not be necessarily observed. A functional etiology should be considered in cases of EPT.