# Hypertrophic olivary degeneration secondary to brain abscess: a case report and literature review

## TL;DR

A rare case of brain abscess leading to a rare neurological condition is reported, highlighting the importance of MRI in diagnosis and management.

## Contribution

This case expands the known causes of hypertrophic olivary degeneration to include bacterial brain abscess.

## Key findings

- A 72-year-old man developed HOD following a brain abscess, with atypical clinical features.
- Multimodal MRI was critical in diagnosing HOD despite the absence of classical symptoms.
- The case underscores the need for increased awareness of HOD in post-infectious neurological deterioration.

## Abstract

Hypertrophic olivary degeneration (HOD) is a rare transsynaptic neurodegenerative disorder arising from disruption of the Guillain-Mollaret triangle (GMT), a neural circuit critical for motor coordination. Classical clinical presentation includes palatal tremor. While cerebrovascular etiology dominates reported cases, HOD secondary to intracranial infections remains poorly characterized, posing diagnostic challenges.

A 72-year-old man with diabetes and hypertension presented with a 7-day history of fever, headache, and vomiting. Initial neuroimaging revealed right cerebellar hematoma with multiple brain abscesses. Antibacterial treatment achieved symptomatic improvement, but follow-up was lost. Seven months later, readmission occurred due to memory decline and personality changes. Magnetic resonance imaging (MRI) showed T2-weighted hyperintensity in the left anterior medulla oblongata and hemosiderosis in the right cerebellar hemisphere. Despite the absence of clinical manifestations of HOD, prior abscess-induced GMT involvement strongly supported the diagnosis. Symptomatic management stabilized the patient, with persistent lesions but no clinical progression at 5-month follow-up.

This case documents a rare case of HOD following bacterial brain abscess, presenting with atypical clinical features. It expands the etiological spectrum of HOD and underscores the need for heightened clinical suspicion in post-infectious neurological deterioration. Multimodal MRI facilitates early diagnosis and timely intervention, highlighting its critical role in managing this underrecognized entity.