Differential Diagnosis

• Single most likely diagnosis:
  • Traumatic Brain Injury (TBI) with acute subdural hematoma: The presence of a large right hemispheric mixed acute subdural hematoma, midline shift, uncal herniation, and descending transtentorial herniation suggests a severe head injury, which is the most likely cause of the patient's condition.
• Other Likely diagnoses:
  • Spontaneous intracranial hemorrhage: Although less likely than TBI, spontaneous intracranial hemorrhage could also cause the observed subdural hematoma, especially in the context of underlying vascular malformations or tumors.
  • Metastatic disease with hemorrhage: Given the patient's history of colon cancer, it is possible that metastatic disease could be contributing to the intracranial hemorrhage, either through direct tumor bleeding or through the development of vascular malformations.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Aneurysmal rupture: Although the CT angiogram did not show any significant aneurysms, it is essential to consider this possibility, as aneurysmal rupture can be catastrophic if not promptly diagnosed and treated.
  • Arteriovenous malformation (AVM): An AVM could be a cause of the subdural hematoma, and it is crucial to rule out this possibility to avoid missing a potentially treatable condition.
  • Hemorrhagic transformation of an ischemic stroke: Although the CT angiogram did not show any significant stenosis or occlusion, it is still possible that the patient had an ischemic stroke that underwent hemorrhagic transformation, which would require prompt diagnosis and treatment.
• Rare diagnoses:
  • Coagulopathy: A coagulopathy, such as disseminated intravascular coagulation (DIC) or a bleeding disorder, could be contributing to the intracranial hemorrhage, although this would be a less common cause.
  • Vasculitis: A vasculitic process, such as giant cell arteritis or primary central nervous system vasculitis, could be causing the subdural hematoma, although this would be a rare and unlikely diagnosis.

The prognosis for this patient is guarded, given the severity of the intracranial hemorrhage and the presence of midline shift, uncal herniation, and descending transtentorial herniation. The patient will likely require prompt neurosurgical intervention to evacuate the hematoma and relieve the mass effect on the brain. The presence of underlying metastatic disease and potential coagulopathy may also impact the patient's prognosis.