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Neuroradiology Case of the Week

Case 357

October 2008

Jonathan R. Wood, BS and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 23-year-old construction worker was standing on a ladder and fell approximately 10-12 feet hitting his head. He briefly lost consciousness but was alert and oriented upon arrival to the emergency department with a complaint of a headache.

Imaging Findings: Cervical spine and head CT were ordered in the emergency department. Contiguous axial tomographic sections of the head and cervical spine were obtained without intravenous contrast. Coronal and sagittal reformats were processed of the cervical spine. There was evidence of a fracture of the right occipital bone at the base of the skull and fluid was seen in the right mastoid air sinuses. A small subarachnoid hemorrhage was appreciated along the right temporal lobe sulcus. The CT of the cervical spine showed no evidence of fracture, dislocation, or subluxation.
     The following afternoon another CT scan of the head was performed due to persistent confusion. Contiguous axial tomographic sections were again obtained from the base to the vertex without intravenous contrast. A new epidural hematoma was noted in the right parietal region not seen in the previous scan measuring 15 mm in maximum thickness by 65 mm in maximum length associated with the fracture in the occipital bone. Minimal air was seen adjacent to the dura and going into the right mastoid air cells suggesting another fracture in the wall of the mastoid. A small left frontal contusion was also noted that had increased in size from the previous scan.

Diagnosis: Delayed Epidural Hematoma

Discussion: An epidural hematoma (EDH) is a collection of blood between the dura mater and the skull usually resulting from a laceration of a meningeal vessel or dural sinus. The most common vessel to be lacerated is the middle meningeal artery as it crosses the thin temporal bone. The hematoma can compress underlying brain tissue leading to damage or herniation which can be fatal. Although epidural hematomas are present in only one to three percent of head injuries, 18% to 30% of patients with an EDH die.
     EDH are often classified as either acute or subacute. Acute EDH are patients with neurological deficits and need surgery within 72 hours of the trauma. Subacute EDH include other patients who do not need immediate surgery or may have a delayed presentation. A delayed EDH is defined as an epidural bleed in which the initial CT scan within the first 24 hours after the trauma is normal but subsequent imagining shows evidence of the EDH. Analysis has shown that 8%-10% of all EDH are delayed making them very rare injuries after a traumatic fall.
     Although a delayed EDH is rare, it demonstrates the importance of repeat CT scanning after head trauma due to the possible high morbidity and mortality of an untreated EDH. Alappat, et al. [1] proposed that repeat CT should always be done after cranial decompression, recovery from shock, or when there is evidence of minimal bleeding on a CT scan. Fankhauser, et al. [5,6] created a list of indications for repeat CT scanning after head trauma which are:

1. After 2-3 days if the first CT shows a fracture with an overlying collection of blood too small for surgical evacuation.
2. In all cases of secondary deterioration.
3. Where there is a secondary elevation of intracerebral pressure.
4. Where there is no clinical improvement.
5. In cases where there is persistent elevation of ICP after evacuation of intracranial hemorrhage.
6. After 12-24 hours for all patients who are paralyzed and ventilated.

The pathophysiology of a delayed EDH is complex because of numerous variables. EDH of arterial origin tend to peak in size around 6-8 hours whereas an EDH of venous origin bleeds more slowly and may take over 24 hours to reach peak size. The ease by which the dura mater separates from the calvarium also affects the evolution of an EDH. Other factors which influence EDH formation are intracranial pressure (ICP) and blood pressure (BP). Low ICP and high BP both allow the EDH to develop faster. Rapid fluid resuscitation can promote a delayed EDH near sites of trauma as well as hyperventilation and mannitol which decrease ICP. Surgical decompression can also precipitate a delayed EDH. One study looked at 47 case reports worldwide of EDH and showed that almost half occurred after a craniotomy to relieve another hematoma, possibly caused by loss of tamponade on a bleeding vessel [5].

References:

1. Alappat JP, Baiju, Praveen, Jayakumar K, Sanalkumar P. Delayed extradural hematoma: a case report. Neurol India. 2002 Sep;50(3):313-5. [PubMed]
2. Kirkpatrick JB, Hayman LA. Pathophysiology of intracranial hemorrhage. In Hayman LA, Taber KH (eds). Nontraumatic Intracranial Hemorrhage. Neuroimaging Clin N Am 1992; 2:11-23.
3. Mishra A, Mohanty S. Contre-coup extradural haematoma: A short report. Neurol India. 2001 Mar;49(1):94-5. [PubMed]
4. Lindenbert R. Pathology of craniocerebral injuries. In Newton TH, Potts DG (eds). Radiology of the Skull and Brain: Anatomy and Pathology, St. Louis, CV Mosby, 1977: 2049-3087.
5. Di Rocco A, Ellis SJ, Landes C. Delayed epidural hematoma. Neuroradiology. 1991;33(3):253-4. [PubMed]
6. Fankhauser H, Uske A, de Tribolet N. [Delayed epidural hematoma. Apropos of a series of 8 cases]. Neurochirurgie. 1983;29(4):255-60. [PubMed]