Revision 20 for 'Rhombencephalitis'

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Rhombencephalitis

Rhombencephalitis (RE) corresponds to inflammatory diseases affecting the hindbrain (brainstem and cerebellum) and has a wide variety of etiologies including infections, autoimmune diseases, and paraneoplastic syndromes with Listeria monocytogenes being cited as the most common cause. RE carries significant morbidity and mortality. 

For a specific discussion, please refer to articles: 

Terminology

It is important to remember that both terms "rhombencephalitis" and "brainstem encephalitis”, despite being used as interchangeable terms, are anatomically different, as the former includes the cerebellum as well as the brainstem

Clinical presentation

Symptoms can vary due to the different causes of RE. When caused by virus it usually presents with headache, vomiting, fever, and ill-defined neurologic symptoms (prodromal stage lasting for about one to two weeks). After that patients develop a spectrum of brainstem symptomatology that could show cranial nerve palsies (it occurs in ~75% of all cases), cerebellar and long-tract motor and sensory deficits.

Pathology

  • infectious

    • viral

      • enterovirus 71: is probably the second most common of infectious RE
      • herpes simplex virus (HSV): is the third most common
        • 80% are caused by HSV1 
        • 20% are caused by HSV2
        • Epstein-Barr virus (EBV)
      • human herpesvirus 6 (HHV6) 
      • Flaviviruses (e.g. West Nile virus and Japanese encephalitis virus)
    • bacterial
      • Listeria monocytogenes: the most common cause of infectious RE
      • Mycobacterium tuberculosis 
      • RickettsiaBorrelia burgdoferiSalmonela typhi,Legionella bozemanii and Mycoplasma pneumoniae are agents that rarely cause encephalitis, but can involve the brainstem. 
  • autoimmune
  • paraneoplastic syndromes: associated with antibodies and, in the majority of cases, having small cell lung cancer as the underlying cause
  • malignancy
    • lymphoma (rare)

Radiographic features

Beam-hardening artifacts limit the visualization of the brainstem on CT images and MRI is the imaging modality of choice for the assessment of patients with suspected pathology in that anatomic location. Protocol should include contrast. 

MRI

When caused by infectious agents, usually RE is presented as:

  • T1: hypo-isointense lesion
  • T2/FLAIR: hyperintense
  • DWI: hyperintense
  • ADC: hypointense
  • spectroscopy: allows differentiation between abscess from tumor
  • T1 C+:     
    • linear cranial nerve enhancement
    • ring enhancement (abscess)
    • heterogeneous if extensive inflammation

Treatment and prognosis

RE require early diagnosis and treatment to avoid neurological sequelae. The morality rate is reported between 10-15% 3

History and etymology

It was first reported by Edwin Bickerstaff and Philip Cloake in 1951 2

The term is derived from the Greek: "rhombos" (lozenge-shaped figure) and "enkephalos" (brain). 

Differential diagnosis

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