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48 YO Male in MVA

Differential Diagnosis

Ischemia

Herpes Simplex Encephalitis

Limbic Encephalitis

Infiltrating Neoplasm- Gliomatosis Cerebri

Epilepsy

Neurosyphilis

Herpes Simplex Encephalitis HSE

Brain parenchyma infection caused by HSV1 typically reactivation in immunocompetent patients

General Imaging Features

Abnormal signal and enhancement of medial temporal and inferior frontal lobes

Location-temporal lobes, insula, subfrontal region and cingulate gyrus. (Limbic System)

The convexities and posterior occipital cortex may become involved

Typically bilateral but asymmetric and spares the basal ganglia.

Rarely affects midbrain and pons (Mesenrhombencephalitis)

CT Findings

Normal in early stage

Low density in temporal lobe and insular regions with mild mass effect.

Earliest findings at 3 days may have patchy gyriform enhancement

Hemorrhage is a late feature

MRI Findings

T1- decreased grey white matter differentiation, and mass effect. May see hyperintensity from acute hemorrhage

T2/FLAIR -Increased signal in grey /subcortical white matter. Edema

DWI- May or may not restrict diffusion

T1+c- May see mild patchy enhancement in gyriform pattern (1 week post infection)

Meningeal enhancement occasionally

MRI finding seen within 2 days of symptoms

Pathology

HSV-1 adults and children

HSV-2 neonates

Etiology

Infection occurs in oronasopharynx through contact with infected secretions

Invades along cranial nerves (lingual nerve a division of trigeminal nerve) to ganglia.

HSV remains dormant and can reactivate by trauma, immunosuppresion, emotional stress,

Incidence 1-3 cases per million

Presentation

Fever, headache, seizures, viral prodrome

Altered mental status, focal or diffuse neurological deficit

May progress to coma or death

HSV uncommon in AIDS

Laboratory

CSF studies show lymphocytic pleocytosis and elevated protein

PCR of csf most useful in diagnosis with specificity and sensitivity of 95-100%

Brain biopsy may be required for diagnosis

Demographics

Highest incidence in adolescents and young adults but occurs at any age

Mortality ranges from 50-70%

Acyclovir iv is treatment

Despite therapy 50% of patients have neurological disabilities such as memory difficulties, hearing loss, epilepsy, personality changes.