Br. J. Surg. Vol. 61 (1974) 307-312

Traumatic pneumocep halus MICHAEL B R I G G S *

SUMMARY The presentation and management of 33 patients with traumatic pneumocephalus have been analysed and two main groups recognized. The first consisted of 12 putients who developed an intracerebral aerocele, the onset of’ which was delayed for up to 52 days from the time of’ injury. These patients presented with signs of raised intracranial pressure which required urgent surgical treatment.

The intrucranial air in the second group was situated in the subdural or subarachnoid spaces and was usually cisible on the first X-ray taken after injury. Adequate early prophylactic antibiotic treatment against menin- gitis was of great importance to these patients, who did not all require surgical intervention.

IN the past confusion has often arisen over the several terms used to describe air inside the cranium; ‘intra- cranial aerocele’, ‘pneumatocele capitis‘ and ‘pneumo- cephalus’ have been used synonymously by different authors. For the purpose of this publication the words ‘intracranial aerocele’ and ‘pneumocephalus’ will be used according to their dictionary definitions, a n aerocele being ‘a tumour formed by air filling a n adventitious pouch’, and pneumocephalus being ‘air within the cranial cavity’ (Dorland, 1965).

The intriguing occurrence of air inside the cranial cavity has received considerable attention in the medical literature; indeed, according to Morley and Hetherington (1957), ‘hardly a year has passed without a t least one report appearing in the medical press, since Luckett, in 1913, first described the roentgeno- logic appearance of air in the ventricle of the brain following fracture of the skull’.

Dandy (1926) reported 3 new cases and collected 25 others from the literature. Rand (1930) reviewed the past literature and presented 8 new cases. A compre- hensive review of the literature o n this subject was later made by Jelsma and More (1954), covering papers from that by Chiari (1 884), which described the post-mortem demonstration of an aerocele in the frontal lobe, to the 4 cases reported in their own article. Morley and Hetherington (1957) described 25 cases of intracranial air occurring in 65 patients with cerebrospinal rhinorrhoea. More recently, Gotham et al. (1965) discussed 14 patients with cerebrospinal rhinorrhoea, 2 of whom had developed hydrocephalus. Markham (1967), in his review of the literature on pneumocephalus, found reference to only 284 cases between 1884 and 1967. Two points which arise from the majority of these publications are that the occur- rence of air in the cranium following trauma is rare and that the air is seldom visible on X-rays taken immediately after the trauma. One of the purposes of

this paper is to show that in the experience of this unit neither of these statements is correct. It is also proposed to demonstrate the clinical differences which exist between intracranial aerocele and other forms of pneumocephalus and to discuss their therapeutic implications. The cases to be analysed are all examples of traumatic pneumocephalus, those resulting from erosion by tumour or the presence of gas-forming organisms have been excluded.

Materials In the 10 years between 1960 and 1970, 15 425 patients with head injury were admitted to the Accident Service of the Radcliffe lnfirmary; of these, 33 had radiological evidence of intracranial air, an incidence of just under 0.2 per cent. This compares with an overall incidence of 0.5 per cent for extradural haematoma in the same unit. Neither of these series is unselected, as patients were transferred to this hospital because of the presence of these lesions, but as the degree of selection is probably much the same for both conditions their incidence may reasonably be compared.

The 33 cases can be divided into two groups according to the site of the air (Table I ) , group 1 consisting of 12 cases in which the air was mainly intracerebral, and group 2, 21 cases where it was extracerebral. It is the type of case in group 1 which has received so much attention in the literature and which is the true aerocele. Those in group 2 can be subdivided according to whether the air was in the subdural or subarachnoid spaces or in the ventricle, but for practical purposes all these cases can be considered together as one group.

Presentation Group 1 In common with the majority of cases previously reported all 12 patients had sustained trauma to the frontal or facial region. This association has been

Table I : SITE OF THE MAJOR VOLUME OF AIR

Site of air No. of cases Group I : lntracerebral 12

Group 11: Subdural 7 Subarachnoid 12 Ventricular 2

Total 33 -

* Department of Neurological Surgery, The Radcliffe Infirmary, Oxford. Present address: Regional Neurosurgical Unit, Brook General Hospital, London SE18.

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the onset of the deterioration coincided with the onset of the rhinorrhoea. At the time of admission or transfer to this service all had some evidence of raised intracranial pressure, usually with signs of localized cerebral hemisphere disturbance. Plain X-rays of the skull a t this time provided the diagnosis. The following case is illustrative.

Case report J. F., a 58-year-old man, was admitted to his local hospital with mild concussion and a linear fracture of his left frontal bone following a road traffic accident. He made a good recovery and was discharged home after 1 week. While at home he remained well apart from some slight frontal headache and mild postconcussional symptoms. Twelve days after the accident he developed cerebrospinal rhinorrhoea; 9 days later his headache became more severe and was associated with a progressive confusion and disorientation. On the day before his admission to this hospital he started to vomit and was incontinent of urine and faeces.

On examination he was drowsy but could be roused easily and appeared to be completely mute. He had no papilloedema but had severe limitation of conjugate upward movements of the eyes and bilateral extensor plantar responses. Skull X-rays revealed a large aerocele in the right frontal lobe pointing down to its site of origin-the ethmoid roof (Fig. I ) . At opera- tion the brain was found to be adherent to the floor of the anterior fossa over the right ethmoid region, where the fistula was situated. The defect was repaired with a piece of temporalis fascia.

Postoperatively, the patient had an uneventful course and

Fig. 1. Right frontal aerocele ‘pointing to’ the ethmoid roof.

Table 11: TIME OF ONSET OF FIRST RHINORRHOEA

Time after injury (d) Group I Group 2

<7 4 15 - 7-14 3

> 14 3 -

Table 111: DURATION OF CEREBROSPINAL FLUID RHINORRHOEA

Duration (d) Group I Group 2 <l 3 8

7-28 5 7 > 28 2 -

Four patients in group 2 and all the patients in group I under- went surgical repair.

noted by many observers (Rand, 1930; Cairns, 1937; Robertson, 1956). Seven of the 12 had, in addition, evidence of severe brain injury, the length of post- traumatic amnesia ranging from 5 days to 3 months. Of the remaining 5 cases, 2 were not concussed and 3 had a post-traumatic amnesia of a few minutes only. No patient in this group had evidence of intracranial air o n the X-rays taken at the time of admission.

The clinical progress of these patients differed in detail but showed marked similarity. All except 2 developed cerebrospinal rhinorrhoea, which persisted until the time of operation. The interval between injury and the onset of rhinorrhoea varied betheen 4 days and 5 weeks (Tables 11,111).

All showed some evidence of recovery from the initial trauma after which there was a slow deteriora- tion, with access in the neurological signs. In 5 cases

was discharged home after 13 days. He was able to return to work as a foundry man 2 weeks later, and in the subsequent 5 years he suffered no long-term ill-effects from his injury.

Group 2 The 21 cases in this group consist of 12 in which the air was in the subarachnoid space, 7 with subdural air (Fig. 2) and 2 in which the initial skull X-ray revealed a spontaneous air ventriculogram. The most striking difference between this group and group 1 is the interval between the injury and the detection of the pneumocephalus; in all but 2 cases the air was visible o n the first X-rays taken after the accident. This is in contrast to the findings of Jelsma and More (l954), who stated that a pneumocephalus ( ? meaning aerocele) is seldom, if ever, visible immediately after injury. Comparison of Tables I V and V, however, will show that while in 19 cases X-ray evidence of pneumo- cephalus was present on the admission films it was not noticed by the admitting medical officer in 8 of these. On one occasion the air was not recognized until 44 days later, and then only retrospectively when the patient was referred to this unit for treatment of chronic refractory meningitis.

Fifteen of the patients in this group developed cerebrospinal rhinorrhoea, all within 7 days of the injury and 12 within the first 24 hours. This persisted for less than 1 week in 7 cases before resolving spon- taneously and for 7-28 days in the remainder.

In common with patients in group 1 a high propor- tion of those in group 2 suffered frontal injuries (17 out of 21), fractures of the facial bones being also present in 10 cases.

The severity of the associated brain injury showed wide variation. Two patients had no evidence of concussion, in 8 the post-traumatic amnesia was less

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a b Fig. 2. An obvious example of subdural pneumocephalus. (i, Anteroposterior view. b, Lateral view.

Table IV: INTERVAL BETWEEN INJURY AND DETECTION OF AIR

Site of air No. of cases Interval (d) between injury and detection of air In tracerebral 12 35 31 52 35 28 31 18 10 42 15 21 21

7 9 3 Subarachnoid 12 I 14 2 0 1 0 0 0 44 Su bdural 7 1 I 0 0 0 4 1 In traven tricular 2 0 0

than 24 hours and in the remaining II the post- traumatic amnesia ranged from 2 days to 10 weeks, 1 patient dying from the effects of the injury 30 days after admission.

Treatment Group I The presence OF an aerocele acting as a space- occupying lesion required urgent surgical treatment for the relief of raised intracranial pressure in all 12 patients. In addition, repair of the fistula was necessary. Whilst awaiting operation these patients were nursed in the supine position and discouraged from blowing their noses to prevent any increase in the size of the aerocele (Bromberg, 1928). Those not already receiving antibiotics were given penicillin and sulphadiazine as a prophylaxis against their develop- ing meningitis. Sulphadiazine is still used because of the facility and speed with which it reaches therapeutic levels against pneumococci and streptococci in the cerebrospinal fluid in patients with non-inflamed meninges (Garrod and O'Grady, 1971). Special inuest&ations: A clue to the site of the fistula was given on most occasions by the shape of the aero- cele, this being that of a pear with its stalk pointing towards the point of entry of the air (Figs. I, 3). On 8 occasions frontal tomograms and Johnson's views (Johnson and Dutt, 1947) were used to obtain more

Table V: DELAY IN RECOGNITION OF AIR

Interval (d) between presence and recognition of air Site of air

Subarachnoid 0 3 0 0 44 0 0 0 1 2 14 1 Subdural 1 4 0 0 0 0 0 Intraventricular 0 0

accurate localization. N o other special investiga- tions were performed preoperatively. Operation: The primary surgical procedure in I 1 cases was frontal craniotomy and intradural explora- tion of the anterior cranial fossa. In all cases the fistula was found. Where there was some doubt, confirmation was obtained by blowing air through the nasal cavity into the cranial fossa which had previously been filled with Ringer's solution; air bubbles were then seen emerging from the fistula (Ommaya et al., 1968). The dural defect having been located it was then patched with either temporalis fascia or fascia lata, depending on its size.

One patient had contracted meningitis by the time of his transfer and it was thought advisable to treat this before craniotomy was undertaken. In order to relieve the intracranial pressure meanwhile the aerocele was tapped through a frontal burr hole. Subsequent treatment was the same as for the other 11 cases.

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5 -

Fig. 3. ‘Pear-shaped’ intracerebral aerocele.

n Group 2

Length of follow-up (yr)

Fig. 4. Length of follow-up of the present series,

Results: Long-term results in these patients depends on the severity of the associated brain injury rather than the presence of the aerocele. From the treatment of this complication the results have been good. Eleven cases had no reaccumulation of air or recur- rence of the cerebrospinal rhinorrhoea. The remaining patient developed a cerebrospinal fluid leak 2 weeks after his first operation, and X-rays revealed a reaccu- mulation of air in the subdural space. At re-explora- tion the fascia1 graft was found to have sloughed. A further repair was successfully carried out. The length of the follow-up of the patients in this group ranges from 6 months to 5 years (Fig. 4).

Group 2 Whilst in group I the intracranial air is of primary importance in that it is acting as a space-occupying lesion, in group 2 the air itself offers no danger to life but is important as a warning of the possible ingress of pathogenic organisms into the cranial cavity. Treatment, therefore, is initially prophylactic against the development of meningitis. Immediately the air was recognized prophylactic treatment was com- menced, consisting of sulphadiazine, 2 g stat. and 1 g 4-hourly, with penicillin, I mega-unit 6-hourly.

Prophylaxis appears to have been inadequate if either the drug dosage was less than this or more than 12 hours had elapsed between the injury and start of treatment. Table VI summarizes the incidence of meningitis in these circumstances. Ten patients were treated adequately and none of these developed meningitis. Prophylaxis was inadequate for one or other of the reasons given above on 8 occasions and 3 of these patients became infected. Three patients received no prophylaxis and all 3 developed meningitis. Although these numbers are small they cannot be ignored.

In all cases the pneumocephalus resolved spon- taneously within 14 days (Table VZI). Operation : Surgical treatment to repair the dural defect was undertaken only when there was persistence of cerebrospinal rhinorrhoea or if the patient had suffered from an attack of meningitis, and was carried out in 6 of the 21 patients. Indication for surgery was present in 3 other cases: one refused to give his consent for operation, one died from broncho- pneumonia 6 weeks after injury, and the third, a man without cerebrospinal rhinorrhoea, remained mori- bund for 10 weeks from chronic meningitis, which was resistant to all treatment, before dying from broncho- pneumonia. Results: The results of surgery have been satisfactory in all 6 cases, there having been no recurrence of cerebrospinal fluid leak or meningitis during a follow-up period of from 6 months to 6 years (Fig. 4). Of the 15 patients who were not operated upon, 2 who died have been mentioned earlier, and an 87-year-old man died 6 days after the accident from his multiple injuries. The remaining 12 have been followed up for periods of up to 4 years and no cases of recurrent cerebrospinal fluid leak or meningitis have been reported.

Discussion Thirty-three cases of traumatic pneumocephalus have been described and i t can be seen that for practical purposes these can be divided into two groups. First there are those with a small amount of air in the subdural or subarachnoid spaces which is usually present from the time of injury, and, secondly, those with a large collection of air in the brain substance,

Table VI: INCIDENCE OF MENINGITIS

Cases of Prophylaxis No. of cases meningitis Adequate 10 0 Inadequate 8 3 None 3 3

Table VII: DURATION OF PNEUMOCEPHALUS IN GROUP 2

Duration :

Subdural 3 4 Subarachnoid 6 6 Intraventricular 2 -

Site of air 1 7 d 7-14d

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the development of which may be delayed for several weeks after injury. It is likely that the mechanisms of air entry differ in these two groups. The traditional explanation (Rizzoli et a]., 1954) of the development of an intracerebral aerocele is perhaps only partly correct. It is that the bony and dural defect resulting from trauma is initially plugged by brain tissue, which in time undergoes colliquative necrosis, allow- ing the egress of cerebrospinal fluid and the ingress of air, the air being forced in when the pressure in the nasal sinuses is raised by acts such as sneezing and nose blowing. Indeed 2 patients in group I described the sensation as ‘something spraying the inside of their head’ whenever they blew their nose. However, it seems likely that in addition to air being forced in it is also sucked in through the fistula by the negative intracranial pressure which may occur when the head is elevated, as may be observed to happen when the ventricle is cannulated with the head in the erect position (Potter, 1971). For this reason patients with cerebrospinal rhinorrhoea have been nursed in the supine position and enjoined to avoid, as far as possible, any act likely to raise the pressure in the paranasal air sinuses (Bromberg, 1928).

It would seem reasonable to evoke suction as the aetiological mechanism in group 2 also. The mechanism postulated is that a t the moment of impact the bony cranium is distorted so as to exert pressure on its contents; in the presence of a suitably situated fracture cerebrospinal fluid would be forced out and air sucked in when the skull returns to its normal shape. As the brain in the area of the fracture would not be necrotic the air would remain in the subarach- noid or subdural spaces. On the 2 occasions when air was seen in the lateral ventricle within I hour of injury it had presumably travelled in the subarachnoid space, through the foramina of Magendie and Luschka into the ventricular system.

Publications on the subject of pneumocephalus have dealt almost exclusively with the group 1 type of case. It IS these patients who tend to find their way to neurosurgical units, either because they are thought to be suffering from a chronic subdural haematoma or because the true diagnosis has been made following X-ray of the skull. Indeed, 8 of the 12 patients in this series were transferred to the Radcliffe Infirmary from surrounding hospitals. There has been little argument concerning the prin- ciples of management of these patients since Dandy described the dural repair in 1926.

However, patients of group 2 type are more likely to be seen in a non-specialized hospital at the time when drug treatment should be started if meningitis is to be prevented. Reference to Fig. 4 wiil reveal the effect of delaying or omitting such treatment. The presence of a few bubbles of air in the subarachnoid (Fig. 5 ) or subdural (Fig. 6) space was overlooked at the time of the admission of half the patients in this series, presumably because this diagnosis had not been considered.

The association between traumatic pneumocephalus and fractures of the frontal and facial bones should

Fig. 5. A small bubble of air in the subarachnoid space.

Fig. 6. A less obvious frontal subdural pneumocephalus.

lead to the careful scrutiny of the X-rays of patients with these injuries for evidence of air in the sub- arachnoid or subdural spaces, particular attention being paid to the region of the chiasmatic and interpeduncular cisterns. Given adequate prophylactic therapy within 12 hours of injury these patients should be spared the complication of post-traumatic meningitis.

With regard to the treatment of the patients in group 2 with a cerebrospinal fistula in addition to the pneumocephalus, the practice in this series has been to operate on those with persistent rhinorrhoea and to treat conservatively those in whom the leak ceased spontaneously within a few days. The debate as to whether all should undergo craniotomy (Calvert and Cairns, 1942; Adson and Uihlein, 1949; Lewin, 1966; Raaf, 1967; Schneider, 1969) will not be entered into at this time. It is by no means certain that all cases require craniotomy, but it must be stressed that adequate conservative treatment includes the pro- phylactic use of penicillin and sulphadiazine for the duration of the cerebrospinal fluid leak.

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