Radiological Hypertrophic Olivary Degeneration Following Posterior Fossa Tumor Surgery.

in World neurosurgery by Kajari Bhattacharya, Pranjal Rai, Aliasgar Moiyadi, Arpita Sahu, Tejpal Gupta, Girish Chinnaswamy, Prakash Shetty, Amit Choudhari, Amrita Guha, Abhishek Chatterjee, Archya Dasgupta, Nitin Shetty, Suyash Kulkarni

TLDR

  • The study looked at a rare condition called hypertrophic olivary degeneration (HOD) that can happen after surgery on the brain. They found that HOD is more common in younger people and that it can take a long time to show up after surgery. They also found that the part of the brain that is most affected by HOD is called the dentate nucleus. The study highlights the importance of recognizing HOD by doctors so that they can diagnose it early and avoid unnecessary tests.

Abstract

Hypertrophic olivary degeneration 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 (ION). 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). A retrospective analysis of patients with PFTs and post-surgical MRI scans was conducted. HOD was diagnosed based on ION signal abnormalities and size changes. Demographics, tumor characteristics, time to HOD onset, involved DROP components, and clinical symptoms were recorded. HOD was seen in 40 (6.2%) patients following PFT surgery. 26 patients were aged 17 or less while the rest were older 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). 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.

Overview

  • The study evaluates the incidence, associated imaging characteristics, potential etiologies, latency period, and temporal progression of hypertrophic olivary degeneration (HOD) in patients undergoing surgical resection of posterior fossa tumors (PFTs).
  • The study uses a retrospective analysis of patients with PFTs and post-surgical MRI scans to diagnose HOD based on inferior olivary nucleus (ION) signal abnormalities and size changes. Demographics, tumor characteristics, time to HOD onset, involved DROP components, and clinical symptoms were recorded.

Comparative Analysis & Findings

  • HOD was seen in 40 (6.2%) patients following PFT surgery. No statistical association was found between the development of HOD and tumor grade (p=0.882).
  • 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).

Implications and Future Directions

  • The study highlights the importance of increased recognition of HOD by neuroradiologists for timely diagnosis and avoidance of unnecessary diagnostic procedures. Future research should focus on identifying potential etiologies of HOD and developing effective interventions to prevent or treat the condition.
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