Learning objectives
Describe the normal anatomy of the Guillain-Mollaret triangle.
Show the MR findingsin hypertrophic olivary degeneration.
Point out MRI sequences for diagnosing in hypertrophic olivary degeneration.
Describe the symptoms of hypertrophic olivary degeneration.
Explain the differential diagnosis of high T2signal in anterolateral part of the medulla area.
Background
Hypertrophic olivary degeneration (HOD) is s a rare condition characterized by unique pattern of trans-synaptic degeneration.
It is usually caused by primary lesions in dento-rubro-olivary pathway (triangle of Guillain and Mollaret).
The triangle of Guillain and Mollarethas three corners (Fig. 1):
Red nucleus
Inferior olivary nucleus
Contralateraldentate nucleus
These corners communicate by tracts; thecentral tegmental tract,
theinferior cerebellar peduncle and thesuperior cerebellar peduncle.
Depending on the location of interruption,
cerebellar atrophy orhypertrophic olivary degenerationcan ensue.
Clinical presentation
The most commonsymptoms are palatal tremor or/and myoclonus,...
Findings and procedure details
MRI findings
We used a MRI (General Electric® 1.5 T) with aprotocol thatincludes axial,
coronal and sagittal T2WI,
coronal FLAIR,
and axial T1WI,
PD,
and T1WI with contrast.
In the initial phase (1-6 months) there is a normal inferior olivary nucleus (ION) on T1WI (no hypertrophy),
but a hyperintense signal on T2WI.
In the later stages (6 months to 3 to 4 years),
we can find hypertrophy of ION ( Fig. 4 ),
isointense to slightly hypointense to gray matter on T1WI,
and increased signal...
Conclusion
Hypertrophic olivary degeneration is a rare disease that is often overlooked when it is not known.
One of the most common causes today is hemorrhaging,
and we must suspect it when we evidence hyperintensity on T2WI sequence in the anterolateral part of the medulla.
Usually patients have new symptoms to those presented during their initial episode of hemorrhage,
ischemia,
trauma or neoplasia in the brain stem.
References
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