Differential Diagnosis in Neurology

16.11. Head Trauma as a Cause of Dementia

• General considerations:
  • Outcome of blunt head trauma depends on:
    • Duration of coma
    • Resolution of post traumatic amnesia
    • 40–50 thousand patients a year in the USA are reported
• Clinical features:
  • Subcortical dementia
  • Ataxia
  • Pyramidal tract dysfunction
  • Parkinsonism
  • Pseudobulbar palsy:
    • Increased gag reflex
    • Bilateral corticospinal dysfunction
    • Dysarthria
    • Emotional incontinence (laughing without mirth and crying without tears)
  • Severe injury:
    • Chronic vegetative state
• Neuropathology:
  • Diffuse (multifocal) brain damage
  • Diffuse axonal injury (DAI)
  • Ischaemic brain damage
  • Brain swelling with increased intracranial pressure
  • Diffuse vascular injury (usually restricted to patients who die shortly after injury)

Distinctive Features of Diffuse Axonal Injury (DAI)

• Diffuse damage to axons (shear line in the centrum semiovale)
• A focal lesion of the corpus callosum (torn in moderate to severe trauma)
• Focal lesions in the dorsolateral quadrant or quadrants of the rostral brainstem
  • Adjacent to the superior cerebellar peduncles

Grade I DAI (Diffuse Axonal Injury)

• Widespread axonal damage:
  • Corpus callosum
  • Cerebral hemisphere white matter
  • Brainstem

Grade II DAI

• Abnormalities noted in Grade I DAI
• Focal abnormalities of corpus callosum associated with small hemorrhage (tissue tear hemorrhage)

Grade III DAI

• All findings of Grade II DAI
• Axonal abnormalities in the rostral brainstem

Dementia of Repeated Head Trauma

• General considerations:
  • Boxers, soccer and football players
• Clinical features:
  • Subcortical dementia
  • Rare dysphasia or dyspraxia
  • "LaBelle" indifference:
    • Inappropriate or no concern for the degree of disability
  • Memory deficits may be out of proportion to physical disability
  • May present with organic brain syndrome
  • Parkinsonian features
  • Ataxia
  • Pyramidal damage
  • Pseudobulbar palsy
• Pathology:
  • Frontal occipital, temporal and parietal bossing area of injury (hemosiderin)
  • Loss of SNPc and Purkinje cells
  • Cortical Neuronal loss
• MRI evaluation:
  • Global atrophy:
    • Commensurate with lesion load
  • Lesions of the corpus callosum
  • Atrophy of frontal occipital and temporal tips
  • Ventricular dilatation