Bilateral middle cerebellar peduncle lesions

LesionsBilateral lesions of boththe middle cerebellar peduncles is, resulting in the middle cerebellar peduncle sign, are uncommon and can be seen either in isolation (rare) or along with other regions of involvement.

Despite their relative rarity, but hasthey have a relativelyfairly long list of differential diagnoses, includingpotential causes (see below) ^1,2-4:. Among these neurodegenerative diseases are probably most common.

Relevant anatomy

The middle cerebellar peduncles are composed of white matter that connects the cerebellar hemispheres to the contralateral pontine nuclei ⁵. Therefore, many of the causes of lesions in this location are related to white matter pathology.

They are supplied by branches of the anterior inferior cerebellar artery and the superior cerebellar artery.

For additional discussion of region anatomy refer to middle cerebellar peduncles.

Radiographic features

Although potentially visible on CT, in most instances this is an MRI feature.

MRI

The majority of patients presenting with bilateral middle cerebellar peduncle lesions have high T2 signal without suppression on FLAIR, with matching low signal on T1 weighted images ⁴. This will usually have facilitated diffusion on ADC maps.

Diffusion restriction (low ADC values) may be seen acutely in infarction and in lymphoma ⁴. Enhancement is usually absent although some enhancement may be seen in lymphoma ⁴.

Causes

Most of the entities listed do not usually cause isolated bilateral middle cerebellar peduncular lesions and as such care must be taken in identifying other areas of involvement.

• neurodegenerative diseases

  • multiple systemic atrophy - cerebellar type (MSA-C)

    • olivopontocerebellar atrophy

    • Shy-Drager syndrome

  • spinocerebellar atrophy

  • fragile X-associated tremor/ataxia syndrome (FXTAS)⁶

  • CARASIL: with involvement of pons; known as the arc sign⁷

  • recessive ataxia

  • ​spinocerebellar ataxia

• metabolic diseases

  • adrenoleukodystrophy

  • Wilson disease

  • acquired non-wilsonian hepatocerebral degeneration

  • hypoglycaemic comaencephalopathy

  • extrapontine myelinolysis

• neoplasms

  • primary CNS lymphoma

  • brainstem glioma

  • leptomeningeal carcinomatosis

• cerebrovascular disease

  • AICAanterior inferior cerebellar artery (AICA) infarction

  • superior cerebellar artery infarction

  • pontine infarct with Wallerian degeneration secondary to pontine infarction ^4,8

  • posterior reversible encephalopathy syndrome (PRES))

• inflammatory and demyelinating diseases

  • multiple sclerosis (MS)

  • acute disseminated encephalomyelitis (ADEM)

  • Behcet disease

  • Erdheim-Chester disease ²

  • neuromyelitis optica spectrum disorder (NMOSD) ⁴

  • progressive multifocal leukoencephalopathy (PML) ⁵

• toxins and drugs

  • cyclosporin-A encephalopathy

  • heroin-induced leukoencephalopathy

• ciclosporin-Ainfective

  • HIV encephalopathy

  • JC virus granule cell neuronopathy

  • Zika virus encephalitis in adults

  See middle cerebellar peduncles for anatomy.