Pneumocephalus is an accumulation of air inside the skull. Air can be located in the cerebral membranes, in the substance of the brain and in its ventricles. Disease occurs as a complication of head injuries, neurosurgical surgical interventions, brain tumors and cerebral infections. Its pathognomonic symptom is the “Hippocratic splash noise”, but often pneumocephalus is hidden behind the symptoms of the underlying pathology. Intracranial air accumulation can be detected using X-ray of the skull, MRI or CT of the brain. Conservative treatment provides therapy for the underlying disease or injury, antibacterial, vascular, neuroprotective, anticonvulsant therapy, the appointment of diuretics and relief of cephalgia. According to the indications, surgical treatment is carried out — puncture drainage of an air cyst, removal of a tumor or inflammatory focus, suturing of the meninges.
General information
The term “pneumocephalus” was first used in 1884. It should be emphasized that pneumocephalus is not a separate nosological unit, it occurs as a complication of traumatic brain injuries, intracerebral tumors and infections, intracranial surgical interventions. Currently, several types of this pathology are distinguished in neurosurgery and neurology. Traumatic form is about 73%, tumor — 12%, infectious — 9%, postoperative – 5%, less than 1% is idiopathic form. Depending on the localization of the air, pneumocephalus is differentiated into subdural, intracerebral and intraventricular. According to the clinical course , pneumocephalus has 4 forms: latent, epileptic, inflammatory, mass form.
Causes
Most often, pneumocephalus develops as a result of traumatic brain injury. In most cases, its cause is a fracture of the walls of the paranasal sinuses (latticed, main, frontal), less often a skull fracture of another localization. However, pathology can also occur with a closed TBI, not accompanied by damage to the cranial bones. The mechanism of its development is associated with a sharp increase in intracranial pressure at the time of injury, which leads to the protrusion of the dura mater into the lattice openings and its rupture. In some cases, pneumocephalus is observed due to a penetrating gunshot wound to the head.
Disease of tumor genesis occurs when the proliferation of tumor tissues leads to the formation of a communication of the cranial box with the external environment. Infectious pneumocephalus is caused by the anaerobic nature of inflammation with the release and accumulation of air bubbles. Often, anaerobic inflammation of cerebral tissues develops against the background of immunosuppression — in the presence of HIV infection, viral hepatitis C, sepsis. Postoperative pneumocephalus is most often noted after surgical interventions on the posterior cranial fossa, especially in patients who underwent surgery in a sitting position.
Pathogenesis
The mechanism of intracranial air penetration may vary. In some cases, this happens once at the time of injury, in others, air is pumped under the dura mater according to the type of valve mechanism in accordance with the phases of breathing, when the victim coughs or sneezes. As a rule, the valve mechanism is observed with subdural localization of the air bubble. Its danger lies in a significant increase in intracranial pressure, leading to a mass effect – displacement of cerebral structures with the danger of the brain stem wedging into the occipital foramen, leading to the death of the patient.
Postoperative form is more often associated with a mechanism called “air from a bottle”. The opening of the meninges with access to the cerebrospinal tract is associated with significant losses of cerebrospinal fluid, which is replaced by air. The structure and location of the brain membranes causes the formation of free cavities filled with air in the subdural space of the frontal region and in the lateral ventricles during liquor loss. Unilateral intraventricular pneumocephalus leads to dislocation syndrome. The phenomenon of an “air bell” may occur when an air bubble from one lateral ventricle prolapses into the second ventricle, blocking the circulation of the cerebrospinal fluid. Bilateral intraventricular pneumocephalus causes a disorder of cerebrospinal fluid circulation with the development of hydrocephalus and intracranial hypertension.
Symptoms
According to some data, in about half of cases, pneumocephalus has a latent course and does not affect the clinic of the underlying pathology in any way. In addition, pneumocephalus has no pathognomonic symptoms. Its clinic depends on the underlying disease, the volume and localization of air accumulation. Headache, vegetative disorders, nausea and vomiting, convulsive syndrome, liquorrhea are mainly noted. The only specific symptom of pneumocephalus is the intracranial “Hippocratic splash noise” that occurs when turning the head. Patients describe it as a feeling of “fluid transfusion” or “gurgling” in the head. However, the “splashing noise” is observed quite rarely.
Postoperative pneumocephalus has a characteristic debut, which consists in maintaining on the 2nd day after surgery a serious condition of the patient that does not correspond to the severity of the underlying disease. Generalized epiprimes, decortication rigidity are possible. The inflammatory form of pneumocephalus is characterized by signs of inflammation of the medulla or cerebral membranes (encephalitis, meningitis, arachnoiditis). In the epileptic form, against the background of depression of consciousness, no deeper than moderate deafening and relatively satisfactory general condition, attacks of Jackson’s epilepsy develop, resistant to antiepileptic treatment. The mass form is characterized by increasing intracranial hypertension with displacement of cerebral structures. Postoperative pneumocephalus is most often manifested by this clinical form.
Diagnostics
Since pneumocephalus has no specific clinical manifestations and in half of the cases its subclinical course is observed, it is almost impossible for a neurologist and a neurosurgeon to diagnose it clinically. The intracranial presence of air can be detected by radiography of the skull. To diagnose the underlying pathology, determine the localization and size of the air bubble, it is advisable to conduct CT or MRI of the brain. CT of the brain reveals subdural, intraventricular or intracerebral accumulation of air (air cyst), the phenomenon of “air bell” can be observed. Infectious pneumocephalus is characterized by the presence of perifocal inflammation on tomograms.
In complex diagnostic situations, the analysis of the cerebrospinal fluid makes it possible to clarify the nature of the underlying disease, against which pneumocephalus developed. If it is necessary to study the cerebrospinal fluid, a lumbar puncture should be performed with extreme caution, since a decrease in intracranial pressure can lead to even greater intracranial air injection and dislocation of brain structures.
Treatment
Strict bed rest is recommended for the patient. Since in most cases pneumocephalus is the result of communication of cerebral structures with the external environment, preventive antibiotic therapy is carried out. With the infectious nature of the disease, etiotropic antibacterial treatment is necessary. Of the broad-spectrum antibiotics, those that are able to penetrate the blood-brain barrier (ceftriaxone, ceftazidim, cefotaxime, cefepim) are used. Vascular therapy (vinpocetine, nimodipine, pentoxifylline) is used to improve air resorption into the bloodstream.
The question remains whether pneumocephalus needs dehydration therapy. Since pneumocephalus is often accompanied by loss of cerebrospinal fluid, some authors recommend rehydration therapy. However, when it is carried out, there is no such replenishment of liquor losses so that it can displace air from the cranial cavity. On the contrary, rehydration is dangerous by increasing the mass effect. But intensive dehydration can also lead to a deterioration of the patient’s condition. Therefore, it is advisable to prescribe diuretic drugs, the effect of which is based on a decrease in liquor production (for example, acetazolamide).
Anticonvulsant therapy (carbamazepine, phenobarbital, diazepam), anti-inflammatory drugs and central electroanalgesia for relief of cephalgia are used as symptomatic treatment. In order to protect and restore cerebral cells as soon as possible, nootropilpiracetam, ginkgo biloba, meldonium, glycine are prescribed.
Disease is subject to surgical treatment in the following cases: with the continuation of intracranial air intake against the background of conservative measures; with a relapse of pneumocephalus; with the formation of a fistula in the dura mater; with the infectious or tumor nature of pneumocephalus. Puncture methods of treatment are widely used — bilateral puncture of the lateral ventricle, subdural puncture of the air cavity. Open surgical techniques include suturing or plastic surgery of the dura mater, removal of a tumor, removal of a brain abscess, etc.
Prognosis and prevention
In some cases, as a result of conservative therapy, independent air resorption occurs. However, pneumocephalus is dangerous by compression of cerebral structures, the formation of dislocation syndrome, intracranial penetration of infection with the development of purulent meningitis, meningoencephalitis. The outcome of pneumocephalus largely depends on the underlying pathology, localization, number and size of intracranial air bubbles. The presence of a single bubble of small size in the shell space, as a rule, has a favorable outcome. The prognosis worsens the multiplicity of blisters, their large size, intracerebral location or intraventricular localization with impaired cerebrospinal fluid circulation.
Prevention of pneumocephalus includes prevention of head injuries, timely treatment of cerebral infections, refusal to perform cerebrospinal punctures for liquorrhea, careful control of the sealing of the intracranial space during operations in the cranial cavity. Some authors propose to conduct intraoperative screening craniography at the final stage of operations, accompanied by the opening of the cerebrospinal tract. This, in their opinion, will immediately allow for the evacuation of the air cavity during its formation.