Case of the Month, January 2019

Submitted by Michael Petry, MD and Thomas Learch, MD

History of Present Illness

A 56 year old woman with a one year history of a ‘medullary mass’ presents for follow-up to her Neurologist. She notes complaints of nystagmus and dizziness and a new complaint of palatal myoclonus (rhythmic, involuntary motions of the soft palate, uvula and larynx). MRI brain with and without contrast is ordered.

Imaging

Sagittal T1 pre-contrast images reveal no abnormalities.

Axial T1 post-contrast imaging of the pontomedullary junction demonstrates an irregularly enhancing vascular-appearing lesion. At this point, the differential has narrowing to capillary telangiectasia, cavernous malformation or a mixed lesion.

Coronal and Sagittal T1 post-contrast images again demonstrate a pontine and medullary irregularly enhancing vascular lesion. The diagnosis is by no means certain but there appear to be characteristics of both capillary telangiectasia and cavernous malformation, so we can describe it as a mixed lesion.

Discussion

Capillary telangiectasias are composed of dilated capillaries with interspersed normal brain parenchyma. Pathologically, they demonstrate thin endothelium without vascular smooth muscle. They are differentiated from cavernous malformations by the presence or absence of normal brain parenchyma and there is some degree of overlap between the diagnoses.

Capillary telangiectasias are primarily infratentorial (brainstem, especially the pons) while cavernous malformations are primarily supratentorial.

Both lesions are angiographically occult as they are composed of capillaries rather than arteries or veins. MRI with contrast is the primary method of diagnosis.

Capillary telangiectasias are ‘do not touch’ lesions as their location (usually brainstem) and natural history makes intervention unlikely to yield benefit. Cavernous malformations on the other hand, occasionally will cause mass effect or hemorrhage. Treatment is surgical resection.

Back to the patient, however:

Axial T2 images at the level of the superior medulla show left superior medullary T2 hyperintensity. Given the mixed capillary telangiectasia and cavernous malformation superior to this region, perhaps there has been some mass effect or disruption of a tract?

In fact, this patient’s lesion lies directly in the central tegmental tract, the connection between the red nucleus superiorly and the inferior olivary nucleus inferiorly. Disruption of this tract by mass effect can result in hypertrophic olivary degeneration, characterized by isolated ipsilateral T2 hyperintensity in the superior medulla in the region of the inferior olivary nucleus.

Typically, the T2 signal increase can last for 3-4 years and hypertrophy follows, lasting another 3-4 years.

The classical symptoms are palatal myoclonus (which this patient demonstrated), as well as rhythmic involuntary movements of the soft palate, uvula, pharynx, larynx and upper extremity. Additional symptoms are ataxia, nystagmus and tremors.

As this is a rare condition, treatment is not well studied but removal or resolution of the lesion is of first priority. In this case, the patient’s lesion is non-treatable. Therefore, treatment should be based on targeting the specific symptoms that the patient is experiencing.

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