A 20-year-old man presented with mild intracranial bleeding, a Horner's syndrome, and left neck swelling following head injury. Following noncontrast CT of the brain, a contrast-enhanced helical CT was performed through the neck that showed a hematoma in the poststyloid space (carotid sheath) with irregular diameter of the ICA. Selective digital subtraction angiography confirmed the presence of left cervical ICA dissection with pseudoaneurysm formation. The aneurysm was resected and an end-to-end anastomosis was done using an inverted saphenous graft. Histology confirmed a diagnosis of traumatic ICA dissection with pseudoaneurysm formation and there was no evidence of pre-existing pathology. Helical CT is a simple, widely available, and relatively non-invasive imaging technique that correlates well with angiography. It should be considered in the evaluation of patients with suspected cervical ICA dissection.