Extradural abscess: causes, symptoms, diagnosis, treatment

An extradural abscess is a collection of pus between the dura mater and the bones of the skull.

Pathogenesis of extradural abscess

An extradural abscess occurs as a result of the spread of the inflammatory process from the mastoid process and tympanic cavity into the cranial cavity and is localized in the posterior or middle cranial fossa. An extradural abscess can develop both in acute otitis and in the exacerbation of chronic purulent otitis media. In such cases, during a radical operation on the ear, cholesteatoma, pus in the tympanic cavity, often destruction of the roof of the tympanic cavity, and when the extradural abscess is localized in the posterior cranial fossa - purulent labyrinthitis are almost always observed.

Symptoms of extradural abscess

The symptoms of extradural abscess are poor, and it is often diagnosed only during surgery. Extradural abscess, which occurs with acute purulent otitis, is often combined with symptoms of mastoiditis. General symptoms are poorly expressed. The main symptom of extradural abscess is abundant purulent discharge from the ear.

A constant symptom of extradural abscess is a mild headache. Headache is localized in perisinusoidal abscess in the occipital and frontal areas, in middle cranial fossa abscess in the squama of the temporal bone, in the postauricular area and in the tragus area. With a deeper location of the abscess, with involvement of the Gasserian ganglion or its branches, trigeminal pain in the face may occur. With extradural abscess and posterior cranial fossa, pain is localized in the neck area. Sometimes with this localization of the abscess, torticollis develops due to pain and dizziness.

Headache in some patients is accompanied by nausea, vomiting, drowsiness. The general condition can be both satisfactory and severe.

Diagnosis of extradural abscess

Physical examination

Body temperature is usually normal or subfebrile even in the presence of a perisinus abscess. A sharp increase in temperature almost always indicates the development of meningitis or sinus thrombosis. Pulse rate usually corresponds to temperature; bradycardia is rarely observed.

During a physical examination of the patient, meningeal symptoms may be detected: mild rigidity of the occipital muscles, Kernig's sign, often more pronounced on the side of the abscess.

Focal symptoms are rare. When localized in the middle cranial fossa, they are in the form of paresis of the opposite limbs, impaired sensitivity in them, focal epileptic seizures. Bilateral paresis usually indicates the involvement of the pia mater in the process. When an extradural abscess is localized in the posterior cranial fossa, nystagmus, coordination disorders in the homolateral limbs, and low muscle tone in them are noted. With a deep location of the abscess descending to the base, paresis of the abducens nerve on the side of the abscess is observed.

Laboratory research

Blood tests are normal. ESR is not increased. Blood changes are observed only in case of extensive pachymeningitis. The composition of the cerebrospinal fluid is usually unchanged.

Instrumental research

The most effective methods for diagnosing extradural abscess are CT and MRI. In the absence of these methods, craniography has not lost its importance.

Craniographic diagnostics of extradural abscesses is based on the detection of indirect radiographic signs, primarily the displacement of the calcified pineal gland. It is determined on craniograms in direct projection, since it is normally located along the midline.

In cerebral angiography, reliable signs of extradural abscesses are the medial displacement, together with the dura mater, of the vessels located on the convex surface of the cerebral hemisphere, from the inner surface of the skull with the formation of an avascular zone.

In CT and MRI, extradural abscesses are diagnosed as a biconvex, flat-concave or crescent-shaped zone of altered density (in CT) and MP signal (in MRI), adjacent to the cranial bones. In this case, pathognomic signs of an extradural abscess are revealed: displacement of the dura mater from the cranial bones. In CT, extradural abscesses usually have an increased density within 60-65 HU.

Differential diagnostics

During surgical treatment of extradural abscess, it is necessary to conduct differential diagnostics with intracerebral and subdural abscesses.

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