Hypertrophic olivary degeneration following surgical resection or gamma knife radiosurgery of brainstem cavernous malformations: an 11-case series and a review of literature

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.

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.

Movement Disorders Associated With Radiotherapy and Surgical Procedures

Occasionally, movement disorders can occur following interventional procedures including but not limited to radiotherapy, dental procedures, and cardiac, cerebral and spinal surgeries. The majority of these disorders tend to be unexpected sequelae with variable phenomenology and latency, and they can often be far more disabling than the primary disease for which the procedure was performed. Owing to poor knowledge and awareness of the problem, delays in diagnosing the condition are common, as are misdiagnoses as functional movement disorders. This narrative review discusses the phenomenology, pathophysiology, and potential treatments of various movement disorders caused by interventional procedures such as radiotherapy and neurological and non-neurological surgeries and procedures.

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.

Brainstem cavernous malformations - no longer a forbidden territory? A systemic review of recent literature

BACKGROUND

Due to its eloquent location and potentially devastating neurological consequences, the management of brainstem cavernous malformations (CCMs) attracts considerable debate. There is currently a paucity of Level 1 evidence for their management. The aim of this literature review is to explore the current evidence on the risk-benefit profile of different management options.

METHODS

A systemic literature search, following the PRISMA algorithm was performed on publications between 2010 and 2018 using the Pubmed database, with the relevant keywords. Only English articles were included. Articles focusing on spinal CCMs and studies with less than 30 participants were excluded.

RESULTS

A total of 222 search results were reviewed and after removal of duplicates and screening of abstracts, 28 clinical papers comprising 30 or more brainstem CCM cases were included in the study. The heterogeneity of the publications precluded a formal meta-analysis of results. The general consensus is that for CCMs presenting with severe symptoms and/or multiple haemorrhages that reach an accessible pial surface, surgery is considered to be the gold-standard treatment, with some authors suggesting the optimal timing to be within two to six weeks of ictus. For those patients with multiple, deep-seated CCM related haemorrhages that do not reach the pial surface, stereotactic radiosurgery (SRS) can be considered. Conservative treatment is generally considered in incidental cases. Management of brainstem cavernomas of other categories still remains controversial.

CONCLUSIONS

Due to their highly eloquent location, brainstem CCMs are challenging lesions to manage. Management must be balanced by the risk-benefit profile and tailored to the individual patients and their treating clinicians. This review provides a comprehensive reference considering all treatment options and provides a basis for evidence-based patient counselling.

Delayed Occurrence of Hypertrophic Olivary Degeneration after Therapy of Posterior Fossa Tumors: A Single Institution Retrospective Analysis

(1) Background: A lesion within the dentato-rubro-olivary pathway (DROP) in the posterior fossa can cause secondary neurodegeneration of the inferior olivary nucleus: so-called hypertrophic olivary degeneration (HOD). The clinical syndrome of HOD occurs slowly over months and may be overlooked in progressive neuro-oncological diseases. Posterior fossa tumors are often located near these strategic structures. The goal of this study was to analyze the systematics of HOD occurrence in neuro-oncological patients. (2) Methods: The neuroradiological database of the university healthcare center was scanned for HOD-related terms from 2010 to 2019. After excluding patients with other causes of HOD, 12 datasets from neuro-oncological patients were analyzed under predetermined criteria. (3) Results: Patients received multimodal tumor treatments including neurosurgery, radiotherapy, and chemotherapy. HOD occurred both unilaterally (left n = 4; right n = 5) and bilaterally (n = 3). Though the mass effect of posterior fossa tumors had already affected strategic structures of the DROP, none of the patients showed signs of HOD on MRI until therapeutic measures including neurosurgery affecting the DROP were applied. HOD was visible on MRI within a median of 6 months after the neurosurgical intervention. In 67%, the presumed underlying surgical lesion in the DROP lay in the contralateral dentate nucleus. (4) Conclusion: In a selected cohort of neuro-oncological patients, therapeutic lesions within the DROP were associated with HOD occurrence.

Ocular Motor and Vestibular Disorders in Brainstem Disease

The brainstem contains ocular motor and vestibular structures that, when damaged, produce specific eye movement disorders. In this review, we will discuss three brainstem syndromes with characteristic ocular motor and vestibular findings that can be highly localizing. First, we will discuss the lateral medullary (Wallenberg) syndrome, focusing on ocular lateropulsion, saccadic dysmetria, and the ocular tilt reaction. Second, we will review the medial longitudinal fasciculus syndrome including the ocular tilt reaction, nystagmus, and the vestibular-ocular reflex. Lastly, we will discuss hypertrophic olivary degeneration and oculopalatal tremor, which may develop weeks to months after a brainstem or cerebellar lesion. In these syndromes, the clinical ocular motor and vestibular examination is instrumental in localizing the lesion.

Surgical Management of Isolated Fourth Ventricular Hydrocephalus Associated with Injury to the Guillain-Mollaret Triangle

BACKGROUND

The occurrence of isolated fourth ventricle and injury to the Guillain-Mollaret triangle in the setting of posterior fossa ependymoma represents a new association. In this case report, we discuss the clinical, theoretical, and therapeutic aspects of this problem. We describe a lateral transcerebellar trajectory and shunt valve configuration for safe fourth ventricle shunting in a patient with prior posterior fossa surgery.

CASE DESCRIPTION

A 45-year-old woman underwent subtotal resection of a fourth ventricle ependymoma (World Health Organization grade III) followed by radiation therapy to control the residual tumor. Her course was complicated by a cerebral abscess and subsequent communicating hydrocephalus, for which she received a lateral ventriculoperitoneal shunt. After placement of the lateral ventricle shunt, there was a progressive increase in the volume of the fourth ventricle over the next 2 years, from 2.5 to 12.0 mL. She developed palatal myoclonus, hand incoordination, bilateral foot numbness, and progressive ataxia. Neuroimaging also revealed hypertrophic degeneration of the inferior olivary nuclei bilaterally. The isolated fourth ventricle was treated by a separate fourth ventriculoperitoneal shunt inserted through a lateral transcerebellar trajectory. A programmable variable pressure valve was implemented.

CONCLUSIONS

Development of an isolated fourth ventricle and injury to the Guillain-Mollaret triangle in the setting of fourth ventricular ependymoma is a newly encountered complication. Choice of treatment modality and timing of intervention should be carefully considered on a case-by-case basis. The data presented in this report may assist in the selection of surgical treatment for isolated fourth ventricle.

Bilateral surgical damage of the central tegmental tract resulting in bilateral hypertrophic olivary degeneration: An MRI case report

Hypertrophic olivary degeneration (HOD) is a rare trans-synaptic neuronal degeneration of the inferior olivary nucleus caused by an injury to the dentato-rubro-olivary connection, also known as Guillain-Mollaret triangle. It leads to hypertrophy of the affected nucleus rather than atrophy and is characterized by hyperintensity on T2-weighted images. Unilateral and bilateral cases are described. We present a case of a 70-year-old patient affected by a tumor inside the fourth ventricle who suffered from diplopia and right seventh cranial nerve palsy. He underwent surgery and developed left seventh cranial nerve palsy. Three months after resection, magnetic resonance imaging revealed the appearance of bilateral HOD. This is the first report of bilateral HOD occurrence after surgical bilateral damage of the rubro-olivary fibers running in central tegmental tracts.

Hypertrophic olivary degeneration in children after posterior fossa surgery. An underdiagnosed condition

BACKGROUND

Hypertrophic olivary degeneration (HOD) is a rare transsynaptic form of degeneration occurring after injury to the dentato-rubro-olivary pathway ("Guillain-Mollaret triangle"). The majority of studies have described HOD resulting from posterior fossa (PF) hemorrhage or infarction. HOD in patients undergoing PF surgery has not been well characterized. These lesions are rare and symptomatic children with HOD are even more uncommon. The purpose of this study was to evaluate HOD that develops after PF operations in children.

MATERIALS AND METHODS

A literature review was carried out describing 37 pediatric cases of HOD in 13 articles. In addition, two new cases of our own experience were included.

CONCLUSIONS

HOD is a rare complication related after PF tumors surgery and symptoms may be misdiagnosed with pediatric cerebellar mutism syndrome. Children with HOD usually do not develop palatal tremor but ataxia is common.

Hypertrophic Olivary Degeneration: Neurosurgical Perspective and Literature Review

BACKGROUND

Hypertrophic olivary degeneration (HOD) occurs because of posterior fossa or brainstem lesions that disrupt the dentato-rubro-olivary tract, well known as the Guillain-Mollaret triangle. Clinical and radiologic hallmarks of this condition are palatal myoclonus and T2 hyperintensity of the inferior olivary complex on magnetic resonance imaging (MRI), respectively. Because symptomatic HOD can complicate the recovery of patients with posterior fossa or brainstem lesions, the purpose of this study is to evaluate clinical and imaging findings of patients with HOD.

METHODS

Sixteen patients (8 female and 8 male) with a mean age of 40.7 years, (range, 5-83 years) years were included in this study based on clinical symptoms and MRI findings.

RESULTS

We reviewed the clinical and imaging findings in 16 cases of HOD at our institution. Seven patients (43.7%) had posterior fossa tumors, 6 patients (37.5%) had cavernoma, 2 patients (12.5%) sustained traumatic brain injury, and only 1 patient (6.2%) had cerebellar infarction. Posterior fossa surgery was performed in 13 (81.2%) of these patients. HOD was detected a mean of 7.2 months (range, 0.5-18 months) after surgery or primary neurologic insult. Unilateral HOD was observed in 10 patients (62.5%), while bilateral HOD was observed in only 6 patients (37.5%). Seven patients (43.7%) were asymptomatic for HOD, whereas 5 patients (31.2%) had symptoms attributable to HOD. Two patients died because of primary tumors, although mean follow-up after detection of HOD on MRI was 52.2 months (range, 1-120 months) in the remaining 14 patients. In these cases, no change in clinical symptoms or imaging findings was detected during follow-up.

CONCLUSIONS

In this series, posterior fossa tumors and cavernomas were the most common causes of HOD. Although most of the patients with HOD remained asymptomatic, HOD complicated the course of recovery in almost one quarter of the patients included in this study. Neurosurgeons should be aware of HOD, which has characteristic clinical and imaging findings. In addition, HOD can complicate the recovery of patients with disruption to the dentato-rubro-olivary tract.

Hypertrophic Olivary Degeneration and Palatal or Oculopalatal Tremor

Hypertrophic degeneration of the inferior olive is mainly observed in patients developing palatal tremor (PT) or oculopalatal tremor (OPT). This syndrome manifests as a synchronous tremor of the palate (PT) and/or eyes (OPT) that may also involve other muscles from the branchial arches. It is associated with hypertrophic inferior olivary degeneration that is characterized by enlarged and vacuolated neurons, increased number and size of astrocytes, severe fibrillary gliosis, and demyelination. It appears on MRI as an increased T2/FLAIR signal intensity and enlargement of the inferior olive. There are two main conditions in which hypertrophic degeneration of the inferior olive occurs. The most frequent, studied, and reported condition is the development of PT/OPT and hypertrophic degeneration of the inferior olive in the weeks or months following a structural brainstem or cerebellar lesion. This “symptomatic” condition requires a destructive lesion in the Guillain–Mollaret pathway, which spans from the contralateral dentate nucleus via the brachium conjunctivum and the ipsilateral central tegmental tract innervating the inferior olive. The most frequent etiologies of destructive lesion are stroke (hemorrhagic more often than ischemic), brain trauma, brainstem tumors, and surgical or gamma knife treatment of brainstem cavernoma. The most accepted explanation for this symptomatic PT/OPT is that denervated olivary neurons released from inhibitory inputs enlarge and develop sustained synchronized oscillations. The cerebellum then modulates/accentuates this signal resulting in abnormal motor output in the branchial arches. In a second condition, PT/OPT and progressive cerebellar ataxia occurs in patients without structural brainstem or cerebellar lesion, other than cerebellar atrophy. This syndrome of progressive ataxia and palatal tremor may be sporadic or familial. In the familial form, where hypertrophic degeneration of the inferior olive may not occur (or not reported), the main reported etiologies are Alexander disease, polymerase gamma mutation, and spinocerebellar ataxia type 20. Whether or not these are associated with specific degeneration of the dentato–olivary pathway remain to be determined. The most symptomatic consequence of OPT is eye oscillations. Therapeutic trials suggest gabapentin or memantine as valuable drugs to treat eye oscillations in OPT.

The dentato-rubro-olivary pathway revisited: New MR imaging observations regarding hypertrophic olivary degeneration

Hypertrophic olivary degeneration (HOD) following a lesion of the dentato-rubro-olivary pathway (DROP) is a well-known imaging finding and has extensively been described in the recent literature. We reviewed our patients with HOD as a result of a lesion of the DROP in order to analyze the disruption of the DROP and the resulting HOD in comparison with the literature. We observed unusual imaging findings in four patients. In two patients it concerned new observations related to the timing and imaging appearances of HOD. HOD became only visible 6 years after a lesion in the red nucleus in one patient and a cystic degeneration of the olivary nucleus was seen 3 years after the HOD in a second patient. In two patients we found HOD that could only be explained by the existence of an afferent feedback loop between the dentate nucleus and the inferior olivary nucleus and by the knowledge that these fibers run through the ipsilateral olivary nucleus before ending in the contralateral olivary nucleus. In one of these patients the lesion was located in the inferior cerebellar peduncle. In the other patient the lesion was located on the midline in the medulla oblongata. The imaging findings in these patients reveal new observations in the stages of imaging appearances in HOD and shed light on the forgotten dentato-olivary afferent feedback loop of the DROP. Clin. Anat. 30:543-549, 2017. © 2017 Wiley Periodicals, Inc.

Hypertrophic olivary degeneration: Case series and review of literature

Hypertrophic Olivary Degeneration (HOD) is a rare neurological condition caused by trans-synaptic degeneration in the brainstem and cerebellum, resulting in varied clinical symptoms, classical being palatal tremors, along with characteristic imaging presentation. Large number of pathologic lesions can cause this condition, ranging from ischemic stroke to neoplasm. The most common conditions include hemorrhage, vascular malformations and infarct. Magnetic resonance scan (MRI) is the imaging modality of choice which shows signal changes with hypertrophy of the inferior olivary nucleus, as well as the primary underlying pathology. Through this pictorial essay, we present the imaging and clinical findings in a number of patients with HOD secondary to varied causes and explain the mechanism behind the changes.

MRI findings of olivary degeneration after surgery for posterior fossa tumours in children: incidence, time course and correlation with tumour grading

PURPOSE

Olivary degeneration is due to many posterior cranial fossa (PCF) lesions affecting the dentato-rubro-olivary pathway, also known as Guillain-Mollaret triangle. Triangle damage results in hyperexcitation and consequently in hypertrophy of the inferior olivary nucleus (ION). The aim of our study was to evaluate the incidence of magnetic resonance (MR) imaging changes in the ION after surgery in a large cohort of paediatric patients and to determine their correlation with tumour grade.

MATERIALS AND METHODS

We retrospectively evaluated 58 patients treated surgically for PCF tumours who underwent MR imaging between 2007 and 2014, 1 week to 5 years after surgery. Histopathology revealed 29 medulloblastomas (WHO IV), 6 ependymomas (WHO II), 2 anaplastic ependymomas (WHO III) and 21 pilocytic astrocytomas (WHO I). ION MR imaging changes were correlated with surgery-to-MR interval and with tumour grading.

RESULTS

ION MR imaging changes were observed in 19/64 (33 %), and all consisted of T2 signal alterations, 15 bilateral and four unilateral, with dentate nucleus damage in all cases. Olivary enlargement was observed in few cases only (7/19). ION T2 hyperintensity was always present between 1 and 6 months after surgery with a trend to decrease, becoming faint after 1 year. The Fisher test demonstrated a significant (p = 0.005) correlation between ION MR imaging changes and high tumour grade.

CONCLUSIONS

Our results demonstrate that olivary degeneration, with or without hypertrophy, is a relatively frequent consequence of posterior fossa surgery, particularly in children treated for high-grade tumours. Knowledge of this condition can prevent misdiagnoses and unnecessary investigations.

A case of hypertrophic olivary degeneration after resection of cavernomas of the brain stem and review of the literature

Hypertrophic olivary degeneration is a transsynaptic form of degeneration, which is also a result of primary or secondary lesion and can damage the dento-rubro-olivary pathway. The dento-rubro-olivary pathway was first described by Guillain and Mollaret and is referred to as "the triangle of Guillain and Mollaret". Multiple factors can destroy the dento-rubro-olivary pathway, such as surgical operation, hemorrhage, tumor, trauma, inflammation, demyelination, degeneration, and radiation damage. All of the above factors can result in delayed hypertrophic olivary degeneration. Articles related to this disease cover etiology, clinical presentation, pathology changes, etc. However, to our knowledge, there has been no literature reporting the use of diffusion tensor imaging and diffusion tensor tractography to improve the diagnosis of hypertrophic olivary degeneration following resection of cavernomas in the brain stem. Herein, we report a case who was diagnosed with hypertrophic olivary degeneration following resection of cavernomas of the brain stem, verify the significance of diffusion tensor imaging and diffusion tensor tractography, and review previous literature. The development of imageology promotes and improves hypertrophic olivary degeneration diagnosis and differential diagnosis.

Hypertrophic olivary degeneration and holmes' tremor secondary to bleeding of cavernous malformation in the midbrain

Background

Hypertrophic olivary degeneration (HOD) is a rare phenomenon, probably related to transsynaptic degeneration of the inferior olivary nucleus. It usually occurs as a response to primary injury of dento-rubro-olivary pathways.

Case report

A young man developed Holmes' tremor 7 months after a cavernous malformation bleed in the midbrain. Typical findings of HOD were observed in the magnetic resonance images: bilateral and asymmetric hypertrophy of the olivary nucleus with slight hypersignal in T2-weighted images. Because of the striking disability related to drug-resistant tremor, the patient underwent stereotactic thalamotomy (nucleus ventralis intermedius of the thalamus/zona incerta) with pronounced functional improvement over time.

Discussion

Disruption of circuits in the Guillain–Mollaret triangle classically results in palatal myoclonus, however midbrain (Holmes') tremor can also occur, as we now describe.