Synonyms:
Global cerebral ischemia a.k.a. global/diffuse cerebral hypoxia ischemia a.k.a. hypoxic ischemic encephalopathy a.k.a. Postanoxic Encephalopahty
Diagnosis:
Clinical features with or without MRI
Clinical features:
- Coma after pulseless cardiac arrest or after significant hypoxia
- Episode of brain anoxia/global ischemia. Myoclonic status epilepticus may occur (may involve face, trunk, limbs)
Findings on investigations:
MRI:
- T2/FLAIR hyperintensity symmetrically both globus pallidi, & caudate nuclei, sometimes cortical.
- Diffusion: restricted in both globus pallidi symmetrically, sometimes cortical.
- T1 hyperintensity in the cortex (laminar necrosis), hyperintensity in both globus pallidi,
EEG features suggesting poor prognosis:
- Burst suppression pattern,
- Periodic discharges associated with myoclonus
- Invariant monorhythmic pattern
- Electrocerebral silence
Pathology:
Gross:
- Diffuse swelling (cytotoxic oedema)
- Softening & discolouration of hippocampus (Somer sector= CA1), watershed areas
Microscopically:
- Hyperacute <12 hours: no changes
- Acute 12-24 hrs: eosinophilic neurons “ischemic change a.k.a. red-dead a.k.a. acute neuronal cell change” especially pyramidal cells of the hippocampus & cerebellum, hyperchromatic nucleus, pyknosis (shrunken nucleus), pallor of neuropil
- Subacute 2 days-2 weeks: macrophages, capillary proliferation, astrocytes
- Chronic months- years: cavitation, macrophages
Investigations to consider:
- CT: to rule out competing diagnosis
- MRI: to rule out competing diagnosis
- EEG: isoelctric pattern, burst-suppression pattern
- Somatosensory evoked potentials SSEP:Bilateral absence of cortical SSEP (N20 component with median nerve stimulation), within 1st week.
Treatment
Therapeutic hypothermia if post Ventricular fibrillation arrest & meets other criteria
Supportive care
Related articles:
- Approach to coma
- Postanoxic myoclonus (Lance-Adams myoclonus)