Bilateral hypertrophic olivary degeneration following surgical resection of a posterior fossa epidermoid cyst

Imaging Features of Hypertrophic Olivary Degeneration

Hypertrophic olivary degeneration (HOD) is a unique form of transneuronal degeneration caused by a disruption of the dentato-rubro-olivary pathway, also known as the triangle of Guillain-Mollaret. The triangle of Guillain-Mollaret is involved in fine voluntary motor control and consists of both the inferior olivary nucleus and the red nucleus on one side and the contralateral dentate nucleus. Clinically, patients classically present with symptomatic palatal myoclonus. Typical magnetic resonance imaging findings include T2-hyperintensity and enlargement of the inferior olivary nucleus evolving over time to atrophy with residual T2-hyperintensity. In this article, we provide a case-based illustration of the anatomy of the Guillain-Mollaret-triangle and the typical imaging findings of hypertrophic olivary degeneration.

Hypertrophic olivary degeneration - a report of two cases

Hypertrophic olivary degeneration (HOD) is seen following lesions in the Guillain–Mollaret triangle. This is unique because the inferior olivary nucleus hypertrophies following degeneration unlike the typical atrophy seen in other structures. We report two cases of HOD in two different clinical scenarios.

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.

MRI and MR tractography in bilateral hypertrophic olivary degeneration

Hypertrophic olivary degeneration is a trans-synaptic neuronal degeneration associated with hypertrophy of the inferior olivary nucleus due to a lesion in the triangle of Guillain-Mollaret. Familiarity with this entity on magnetic resonance imaging (MRI) is essential to avoid other erroneous ominous diagnoses. We present a case of bilateral hypertrophic olivary degeneration and discuss the etiopathogenesis and MRI findings in this entity. The contributory role of MR tractography in the diagnosis is also highlighted.

Hypertrophic olivary degeneration with gadolinium enhancement after posterior fossa surgery in a child with medulloblastoma

Hypertrophic olivary degeneration (HOD) is a rare transsynaptic form of degeneration occurring secondary to the disruption of the dentato-rubro-olivary pathway ("Guillain-Mollaret triangle"). HOD can be caused by ischemic, hemorrhagic, traumatic, or neoplastic lesions, and it can also occur following posterior fossa surgery. MRI characteristics of HOD include T2 signal increase and hypertrophy. To date, blood–brain barrier disruption has not been reported in HOD. Here, we present the first case of HOD with temporary gadolinium enhancement in a 10-year-old child 7 months after resection of a posterior fossa medulloblastoma. The recognition of gadolinium enhancement as a radiological feature of HOD may help to distinguish between this benign secondary condition and tumor recurrence.

Frequency of bilateral hypertrophic olivary degeneration in a large retrospective cohort

BACKGROUND AND PURPOSE

Hypertrophic olivary degeneration (HOD) is an uncommon type of transneuronal degeneration. Case reports and case series described in the literature provide a foundation of our current knowledge of HOD. These reports have described HOD most frequently to be unilateral and occurring in association with lesions in the dentato-rubro-olivary pathway. Our purpose was to evaluate the rate of bilateral versus unilateral HOD in a large case series.

METHODS

A retrospective review was performed to identify patients in which the phrase "hypertrophic olivary degeneration" occurred in the radiology report. A diagnosis of HOD was confirmed on imaging if there was focal hyperintensity on T2-weighted images confined to either or both inferior olivary nuclei.

RESULTS

A total of 102 patients had findings consistent with HOD. Of these, 76% had findings bilaterally. In 44%, a lesion could not be identified to explain HOD. Bilateral HOD was common in both lesional and nonlesional group, though more common in the nonlesional group.

CONCLUSION

This study demonstrates that HOD is frequently bilateral. In slightly over 50% of patients with HOD, a lesion can be identified. In just under 50% patients with HOD, a lesion could not be identified and in these cases HOD was present bilaterally in the majority.

MR imaging evaluation of inferior olivary nuclei: comparison of postoperative subjects with and without posterior fossa syndrome

BACKGROUND AND PURPOSE

Posterior fossa syndrome is a severe postoperative complication occurring in up to 29% of children undergoing posterior fossa tumor resection; it is most likely caused by bilateral damage to the proximal efferent cerebellar pathways, whose fibers contribute to the Guillain-Mollaret triangle. When the triangle is disrupted, hypertrophic olivary degeneration develops. We hypothesized that MR imaging patterns of inferior olivary nucleus changes reflect patterns of damage to the proximal efferent cerebellar pathways and show association with clinical findings, in particular the presence or absence of posterior fossa syndrome.

MATERIALS AND METHODS

We performed blinded, randomized longitudinal MR imaging analyses of the inferior olivary nuclei of 12 children with and 12 without posterior fossa syndrome after surgery for midline intraventricular tumor in the posterior fossa. The Fisher exact test was performed to investigate the association between posterior fossa syndrome and hypertrophic olivary degeneration on MR imaging. The sensitivity and specificity of MR imaging findings of bilateral hypertrophic olivary degeneration for posterior fossa syndrome were measured.

RESULTS

Of the 12 patients with posterior fossa syndrome, 9 had bilateral inferior olivary nucleus abnormalities. The 12 patients without posterior fossa syndrome had either unilateral or no inferior olivary nucleus abnormalities. The association of posterior fossa syndrome and hypertrophic olivary degeneration was statistically significant (P < .0001).

CONCLUSIONS

Hypertrophic olivary degeneration may be a surrogate imaging indicator for damage to the contralateral proximal efferent cerebellar pathway. In the appropriate clinical setting, bilateral hypertrophic olivary degeneration may be a sensitive and specific indicator of posterior fossa syndrome.

Hypertrophic olivary degeneration after surgical resection of brain tumors

BACKGROUND

Hypertrophic olivary degeneration (HOD) can be seen as high signal intensity with enlargement of the inferior olivary nucleus (ION) on T2-weighted magnetic resonance (MR) images 4-6 months after injury of the Guillain-Mollaret triangle. To the best of our knowledge, there has been no systematic evaluation with regard to the relationship between neurosurgical intervention affecting this pathway and the appearance of HOD.

PURPOSE

To evaluate MR findings of HOD after surgical resection of brain tumors with the temporal evolution in focus.

MATERIAL AND METHODS

MR images of seven patients that showed signal changes in the ION after surgical resection of brain tumors in the posterior fossa were retrospectively reviewed. T1-weighted imaging with and without gadolinium (Gd) contrast enhancement and T2-weighted imaging were performed in all patients before and after surgery.

RESULTS

Before surgery, no patient had a signal change in the ION. T2-high signal intensity of the ION initially appeared 5 days to 2.5 months after surgery. Five patients showed enlargement of the ION with T2-high signal intensity 11 days to 3.5 months after surgery: three patients showed the enlargement of the ION subsequent to the T2-signal change on serial follow-up MR images. On Gd-enhanced T1-weighted images, there was no enhancement at the ION in any patient. Each signal change of the ION was consistent with HOD, according to the relationship between the resection site of the tumor and the Guillain-Mollaret triangle on follow-up MRI.

CONCLUSION

HOD can be caused after neurosurgical intervention of brain tumors involving the Guillain-Mollaret triangle. It is important for radiologists to distinguish HOD from tumor recurrence.

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

BACKGROUND

We describe 11 patients with hypertrophic olivary degeneration (HOD) after surgical resection or gamma knife radiosurgery for brainstem cavernous malformations. In addition, we statistically analyzed the predicting factors associated with the development of HOD.

METHODS

From January 2001 to May 2011, a total of 73 patients (30 in the surgical group and 43 in the radiosurgery group) with brainstem cavernous malformations were treated in our institute. Of them, 11 patients (incidence: 15 %) developed HOD with high signal intensity on T2-weighted MRI during follow-up. The predicting factors (location, size, age, and treatment method) associated with the development of HOD were statistically analyzed.

RESULTS

Among the 11 HOD patients, seven patients received surgical resection and four patients received gamma knife radiosurgery. Six patients had bilateral HOD and the remaining five patients had unilateral HOD. Overall HOD-associated symptoms presented in four patients, including three palatal tremors and one ataxia. In all four patients with symptoms, these symptoms disappeared incompletely within the clinical follow-up period. The size of the cavernous malformation, age of patient, and treatment methods were not significantly correlated with the development of HOD. A significantly higher incidence of HOD was associated with midbrain cavernous malformations than with pontine or medulla cavernous malformations.

CONCLUSIONS

HOD should be recognized as a non-infrequent complication of surgical resection or gamma knife radiosurgery within the brainstem, especially for midbrain cavernous malformations. In addition, to the best of our knowledge, this is the first report on HOD development after radiosurgery.

Collision in the inferior olive: hypertrophic olivary degeneration complicated by radiation necrosis in brainstem primitive neuroendocrine tumor

Hypertrophic olivary degeneration (HOD) is caused by disruption of the triangle of Guillain and Mollaret. We describe a child with a primitive neuroendocrine tumor who developed an expansile nonenhancing lesion in the olive after surgery and radiation therapy. Diffusion tensor imaging and tractography showed disruption of the central tegmental tract consistent with HOD. Subsequent transient enhancement of the olive was consistent with early radiation injury. Knowledge of coexisting complications such as HOD and radiation injury is essential for proper management.