E1482. Armed With a Differential: An Imaging Approach to Lesions of the Brachium Pontis
  1. Steven Krausz; Montefiore Medical Center
  2. Elliot Shulman; The Albert Einstein College of Medicine
  3. Shira Slasky; Montefiore Medical Center
  4. Andrew McClelland; Montefiore Medical Center
  5. Judah Burns; Montefiore Medical Center
The brachium pontis (BP), or middle cerebellar peduncle, is the major afferent white matter tract of the cortico-ponto-cerebellar pathway carrying fibers from the contralateral pontine nuclei to the cerebellum. Lesions of the brachium pontis produce variable clinical symptoms including diplopia, dysphagia, dysarthria, dysmetria, deafness, vertigo, emesis, ataxia, palsy, and weakness. Insults affecting the brachium pontis can result from a broad differential and are not limited to classical white matter diseases. Magnetic resonance imaging findings aid in narrowing the differential and can suggest specific etiologies.

Educational Goals / Teaching Points
The educational goals of this presentation are to learn the functional neuroanatomy of the middle cerebellar peduncles and recognize key pathologies which may affect this anatomic region. We will highlight the anatomical relationship between associated white matter pathways and adjacent structures. Using a case-based approach, we will demonstrate a range of differential considerations for lesions of the brachium pontis. We will highlight specific imaging features and localizing cues which can be used to differentiate between common and uncommon lesions.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Brachium pontis lesions can derive from multiple etiologies including demyelinating, inflammatory, neoplastic, toxic/metabolic, cerebrovascular, infectious and degenerative diseases. Even lesions deriving from the same etiology can be differentiated by characteristic imaging features and localizing cues. Demyelinating lesions can be intrinsic to the BP as in multiple sclerosis, or occur through extension from the pons such as in central pontine myelinolysis. Cerebrovascular lesions can result from direct ischemia of the anterior inferior cerebellar artery or as a sequelae of an insult elsewhere such as in Wallerian degeneration secondary to a pontine infarct. Metabolic diseases can also cause direct damage such as in adrenoleukodystrophy or result from a metabolic insult elsewhere such as in crossed cerebellar diaschisis and atrophy. Neoplastic lesions may often appear unilateral while some toxic lesions such as solvent abuse may appear bilaterally. Degenerative diseases such as sporadic olivopontocerebellar atrophy may also appear as a symmetric hyperintense lesion on T2-weighted MR and will also exhibit atrophy.

The brachium pontis is affected in many pathological processes. Awareness of these different processes as well as their typical imaging characteristics is important in creating and narrowing a differential diagnosis of lesions in the middle cerebellar peduncles.