Acute hemorrhagic leukoencephalitis

Acute hemorrhagic encephalomyelitis (AHEM), also known as acute hemorrhagic leukoencephalitis (AHLE), Hurst disease or Weston Hurst syndrome, is a very rare form of demyelinating disease. It occurs sporadically and may be considered as the most severe form of acute disseminated encephalomyelitis (ADEM) and is characterized by an acute rapidly progressive fulminant inflammation of the white matter. The cause is unclear but may be post-infectious (either viral or bacterial).

Epidemiology

AHEM may more commonly occur in young adults, contrary to ADEM, which is more commonly diagnosed in children ⁵. It has been reported in older adults ⁶. There is no gender predilection.

Clinical presentation

Patients present with fever, neck stiffness, fatigue, headache, nausea and vomiting, seizures and coma.

A history of upper respiratory infection prior to presenting neurologic symptoms (interval 2 to 12 days) may be present in ~50% of cases ⁴.

Pathology

AHEM is related to autoimmune cross reaction to the myelin antigens, and is defined by the presence of necrotizing venulitis with perivascular hemorrhages, diffuse CNS ischemic lesions and myelin destruction ⁴. Many authors consider it a fulminant variant of ADEM, forming a spectrum of disease ^4,5.

Macroscopic appearance

• marked cerebral edema and congestion, often with herniation
• punctate hemorrhages within the cerebral white matter, not infrequently necrotic
• not uncommonly presence of necrosis in basal ganglia
• typically no involvement of the spinal cord

Microscopic appearance

Imaging appearances are dominated by fibrinoid venous necrosis, leading to acute hemorrhage with fibrin exudates and neutrophilic debris:

• classically hemorrhages around the necrotic venules resembling “ring and ball”
• white matter ischemic changes adjacent to necrotic postcapillary venules
• hemorrhage more prominent than demyelination
• no specific immunohistochemical pattern ⁴

Radiographic features

MRI

This is the gold-standard and may depict aforementioned morphologic changes such as:

• large tumefactive lesions involving the white matter and sparing the cortex
• associated punctate hemorrhages and extensive mass effect and surrounding edema.
• possible involvement of ganglia and thalami

Detection of cerebral microhemorrhages by GRE or the more sensitive susceptibility weighted images (SWI) is an important finding and may allow for differentiation from ADEM.

Treatment and prognosis

Acute hemorrhagic leukoencephalitis is associated with a very poor prognosis with the majority of affected individuals succumbing to the disease.

History and etymology

It was first described by Edward Weston Hurst (1900-1980), a British neurologist, in 1941 ².

Differential diagnosis

General imaging differential considerations include:

• acute disseminated encephalomyelitis (ADEM): probably the milder form of the same disease
• severe demyelination / multiple sclerosis
  • tumefactive demyelinating lesions (TDL)
  • acute malignant Marburg type multiple sclerosis
• herpes simplex encephalitis
• cerebral vasculitis