In which spaces of the head are the epidural abscess and the subdural abscess?
Intracranial epidural abscess is between the inner table of the skull and the dura mater. Subdural abscess is beneath the dura, in the potential subdural space.
How do infections enter the epidural space?
Infections may enter the epidural space by hematogenous/lymphatic seeding from a remote site or by direct extension from a contiguous site.
Which one can cross the midline, epidural abscess or subdural abscess?
Subdural empyemas do not cross the midline. On the other hand, epidural empyemas may extend across the midline in the frontal region, a finding that helps distinguish the epidural disease from the subdural disease.
What are the clinical signs and symptoms of intracranial epidural empyemas?
Signs and symptoms can happen because of increasing intracranial pressure or because of infection. Therefore, clinical symptoms include fever, headache, lethargy, nausea, vomiting, photophobia, and altered mental status; and signs are sinus drainage, cranial nerve palsies, focal neurologic deficits, meningismus, seizures, hemiparesis, altered mental status, and papilledema.
What are the radiological features of an epidural abscess?
Imaging studies in intracranial epidural empyemas show crescentic or lentiform extra-axial fluid collections, which are low density on CT and mildly hyperintense compared to CSF on T2 - weighted MRI, with a surrounding membrane that enhances with contrast administration. The mass effect on the adjacent parenchyma promotes inward displacement of cortical vessels, may efface the cortical sulci, and may cause a midline shift to the contralateral side. There are usually changes in the adjacent brain parenchyma, that may represent a reaction edema or an associated cerebritis. Cortical vein thrombosis with venous infarction may occur. Diffusion-weighted MR images usually demonstrate restricted diffusion.
MRI shows the multiloculate morphology of the intracranial epidural collection located in the right supraorbital region; the largest loculation measures 3.5 x 2.7 x 2.1 cm, with a volume of 10.3 cm3. This collection is hypointense on T1-weighted and hyperintense on T2-weighted images, with a surrounding membrane that enhances with contrast administration. The collection shows restricted diffusion most pronounced within the posterior loculation. There is edema in the right frontal lobe, with mass effect and partial compression of the frontal horn of the right lateral ventricle.
There is also right ethmoidal sinus inflammation and the relationship of the collection to the right ethmoid cells. Neurosurgical drainage confirmed intracranial epidural abscess.
An arachnoid cyst is present in the left middle cranial fossa, with CSF intensity, no solid component, and no enhancement.
There are several confluent focal areas of signal intensities (FASI) in the cerebellum and some minor lesions in the basal ganglia,