Rhombencephalitis

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

For a specific discussion, please refer to articles: 

• Listeria rhombencephalitis
• tuberculous rhombencephalitis
• paraneoplastic rhombencephalitis

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 RErhombencephalitis. When caused by a virus it usually presents with headache, vomiting, fever, and ill-defined neurologicneurological symptoms (prodromal(the prodromal stage lasting for about one to two weeks). After that patientsSubsequently, patients develop a spectrum of brainstem symptomatology that could showsuch as cranial nerve palsies (occur in ~75% of all cases), and cerebellar and long-tract motor and sensory deficits.

Pathology

• infectious

  • viral

    • enterovirus 71: is probably the second most common of infectious RErhombencephalitis
    • 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 RErhombencephalitis
    • Mycobacterium tuberculosis
    • Rickettsia, Borrelia burgdoferi, Salmonela typhi,Legionella bozemanii and Mycoplasma pneumoniae are agents that rarely cause encephalitis, but can involve the brainstem. 
• autoimmune
  • Behçet disease (most common autoimmune cause)
  • multiple sclerosis
  • systemic lupus erythematosus
• 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 visualizationvisualisation of the brainstem on CT images and MRI is, with contrast, 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, rhombencephalitis usually RE is presented ashas the following signal characteristics:

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

Treatment and prognosis

RE requireRhombencephalitis requires 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

• brainstem tumour