1. Bilateral Injuries to the Triangle of Guillain-Mollaret
Daniel Chow, MD
Jared Narvid, MD
William Dillon, MD

2. Disclosures
The authors have no disclosures.

3. Background
The Triangle of Guillain-Mollaret
The triangle of Guillian-Mollaret, also known as the myoclonic triangle, is feedback circuit for regulating spinal cord motor activity.
Injury to triangle is associated with stereotypical palatal myoclonus
(involuntary soft palatal musculature rhythmic movements)

4. Background Triangle of Guillain-Mollaret Pathway
The three corners of the triangle:
Ipsilateral red nucleus
Ipsilaterla inferior olivary nucleus
Contralateral dentate nucleus
Red Nucleus
Red Nucleus
Superior
Cerebellar
Peduncle
Dentate Nucleus
Central
Tegmental
Tract
Inf. Olivary Nucleus
Dentate Nucleus
Inferior
Cerebellar
Peduncle
Inf. Olivary Nucleus

5. Background
Purpose
We report a unique case of injuries to the dentatorubro-olivary pathway bilaterally in a single patient with both:
Hypertrophic olivary
Deafferentation changes in the dentate.
Red Nucleus
Dentate Nucleus
Inf. Olivary Nucleus

6. Case Report Presentation
A 63-year-old male with past medical history significant for prior right pontine hemorrhage was referred to our institute for follow-up imaging.
Evaluation of MR imaging at time of the hemorrhage demonstrated a right pontine hemorrhage in the region of the right:
Central tegmental tract
Superior cerebellar peduncle
Axial susceptibility-weighted MRI demonstrates a right pontine hemorrhage

7. Case Report Follow-up (4 months)
MRI obtained 4 months later, revealed both:
Hypertrophy of the right olivary nucleus
Atrophy and high signal of the right dentate nucleus

8. Case Report Comparison to prior imaging
Follow-up MRI 4 months later reveals ipsilateral hypertrophy of the right inferior olivary nucleus (C) as well as atrophy and T2 hyperintense signal of the right dentate
Coronal T2 image at time of hemorrhage demonstrates normal appearing inferior olivary nucleus and dentate
Follow-up MRI 4 months later reveals new ipsilateral hypertrophy of the right inferior olivary nucleus as well as atrophy and T2 hyperintense signal of the right dentate

9. Discussion Pathway for Hypertrophic Olivary Denervation
Injury to the pathway resulting in hypertrophic olivary denervation is well established:
Injury to efferent central tegmental tract may result in hyperexcitation
Subsequent hypertrophy of the ipsilateral inferior olivary nucleus.

10. Discussion Pathway for Atrophy of the Contralateral Dentate
In our case however, a heretofore underappreciated change also was seen consisting of abnormal signal and atrophy of the ipsilateral dentate nucleus:
Injury to afferent superior cerebellar peduncle tract
Subsequent atrophy of the ipsilateral dentate nucleus.

11. Discussion
Summary
Familiarity with these pathways are important for the neuroradiologist for accurate diagnosis.

12. References
Kitajima M, Korogi Y, Shimomura O, et al. Hypertrophic olivary degeneration: MR imaging and pathologic findings. Radiology. 1994; 192:539-43
Kim SJ, Lee JH, Suh DC. Cerebellar MR changes in patients with olivary hypertrophic degeneration. AJNR Am J Neuroradiol. 1994; 15:1715-9