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British Journal of Radiology (2007) 80, e301-e304
© 2007 British Institute of Radiology
doi: 10.1259/bjr/20935250
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Case report

Pneumocephalus as a complication of diverticulitis

S Shetty, FRCR 1 J Aw, FRCR 1 and C Cook, FRCR 2

1 Bristol Royal Infirmary, 2 Weston General Hospital, Bristol Royal Infirmary, Marlborough Street, Bristol BS1 3NU, UK

Correspondence: Dr Shilpa Shetty, Specialist Registrar, Radiology, Bristol Royal Infirmary, Marlborough Street, Bristol, North Somerset BS1 3NU, UK. E-mail: shilpashetty{at}doctors.org.uk


   Abstract
Top
 Abstract
Case report
 Discussion
 Conclusions
 References
 
We report a case of pneumocephalus, as a complication of diverticulitis, in a 48-year-old man who presented with back pain and mild disorientation. There are no previous reports of diverticulitis causing this phenomenon.


   Case report
Top
 Abstract
 Case report
Discussion
 Conclusions
 References
 
A 48-year-old unemployed man presented with a 4 week history of back pain, intermittent fever and rigors and mild disorientation. He had no other neurological symptoms. There were no lower urinary tract symptoms, nor any history of altered bowel habit. He had a previous medical history of depression and anxiety and was on amytriptylline. He had been prescribed amoxycillin and dihydrocodeine by his general practitioner. On clinical examination, he was tender in the suprapubic area and had left loin tenderness. His Glasgow Coma Scale score was 15/15 and he had a normal CNS examination but he had a mini-mental test score of 6/10. Initial blood tests showed a creatinine level of 193 µmol l–1 (normal level 55–150 µmol l–1), urea 19.4 mmol l–1 (2.5–6.6 mmol l–1), white blood count 17.4x109 l–1 (4–11x109 l–1; neutrophils 15.3x109 l–1), haemoglobin 10.6 g dl–1 (14.0–17.7 g dl–1) and C-reactive protein (CRP) 341 (<10).

A provisional diagnosis of pyelonephritis was made and he was treated with intravenous fluids and ciprofloxacin. To evaluate his symptom of vagueness, a CT scan of his brain was performed. This showed gas within the ventricular system (Figure 1Go). There was no history of trauma, lumbar puncture, sinusitis or surgery as possible causes of this finding. A CT scan of the abdomen and pelvis was then performed to determine a cause for the abdominal tenderness. This scan showed bilateral hydronephrosis (Figure 2Go) and a 6.5x3 cm pre-sacral abscess adjacent to the recto-sigmoid junction (Figure 3Go). There was gas in the retroperitoneum, in the sacral foramina (Figure 4Go) and also within the spinal canal at multiple levels (Figure 5Go).


Figure 1
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  		Figure 1. Axial CT of the brain with gas in the anterior horns of the lateral ventricles.

 

Figure 2
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  		Figure 2. Axial CT through the abdomen demonstrating bilateral hydronephrosis and gas within the spinal canal.

 

Figure 3
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  		Figure 3. Axial CT through the pelvis with gas in the pre-sacral region and the sacral foramina.

 

Figure 4
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  		Figure 4. Axial CT through the pelvis demonstrating the pre-sacral abscess.

 

Figure 5
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  		Figure 5. Axial CT at vertebral level T10 showing gas within the spinal canal.

 
The pre-sacral abscess was drained surgically. The recto-sigmoid was mobilized to reveal a pre-sacral abscess, and the involved segment of recto-sigmoid was resected. A segment of distal small bowel related to the abscess was thickened and had three small perforations; therefore, this segment of the small bowel and the caecal cuff was resected. Hence, the patient had a left iliac fossa end colostomy and a right iliac fossa ileostomy. At surgery, there was no sacral involvement. Macroscopically, the specimen of sigmoid colon demonstrated two fistulae 5 mm apart, extending all the way out to the external surface of the specimen. Microscopically, it showed diverticulosis with some inflamed diverticula. No malignancy was demonstrated and the overall features were indicative of complicated diverticular disease. Blood cultures grew Streptococcus milleri and anaerobic organisms. The pre-sacral abscess swabs grew Streptococcus milleri and mixed coliforms (sensitive to penicillin, cefataxime, ciprofloxacin and gentamicin). The patient made a good recovery post-operatively and was discharged home on antibiotics.


   Discussion
Top
 Abstract
 Case report
 Discussion
Conclusions
 References
 
This case describes the finding of pneumocephalus secondary to diverticulitis. Pneumocephalus, the presence of air or gas within the cranial vault, is caused by a disruption of the dura allowing abnormal communication and air introduction into the brain [1]. Intracranial air can occur in any compartment (epidural, subdural, subarachnoid, parenchymal, intraventricular or intravascular). The diagnosis and location of intracranial air can be made easily on CT, with intraventricular air being the least common [1, 2]. Traumatic head injuries are the most common cause, usually fractures of the paranasal sinuses or compound base of skull fractures [1]. Tension pneumocephalus, the accumulation of intracranial gas under pressure, is a rare but potentially life-threatening condition that can complicate craniofacial surgery, trauma or cranial tumour. It presents as an acute or subacute expanding mass lesion, which requires prompt neurosurgical intervention [3]. Iatrogenic causes are most frequently due to neurosurgical procedures [4]. Neoplastic invasion of the sinuses, mastoiditis or sinusitis are known causes.

Other rare causes of pneumocephalus include as a complication of radiotherapy, secondary to osteonecrosis [5], intravenous catheterization [6], pipe smoking [7] and post-epidural procedures [8]. Further to this, spontaneous pneumocephalus has been described following elective thoracotomy secondary to dural tear [9], subarachnoid pleural fistulae [10, 11] and pneumoencephalomenigitis secondary to infected lumbar arthrodesis with a fistula [12], and as "spontaneous" pneumocephalus associated with enteric organisms isolated from the cerebral spinal fluid [13]. We have found no documentation of pneumocephalus caused by diverticulitis.

Diverticular disease of the colon is an acquired herniation of the mucosa and submucosa through the muscle layers secondary to high pressure contractions during colonic segmentation [14], predominantly affecting the left colon. It is very common in developed countries with a reported incidence of 5–10% in the fifth decade, increasing to almost 80% by the age of 80 years [15]. Most patients are asymptomatic, whereas others experience vague left-side abdominal pains and altered bowel habit. The initial attack usually settles with bowel rest and antibiotics. Greater than 70% of patients with symptoms will have recurrent episodes and 30% will eventually require surgery [16].

Diverticulosis describes the presence of diverticula. Diverticulitis implies superimposed inflammation of a diverticulum, especially of the small pockets in the wall of the colon that fill with stagnant faecal material and become inflamed. The term diverticular disease encompasses both concepts. The complications of acute diverticulitis include pericolic fat inflammation in 98% of cases, colon wall thickening in 70%, pericolic abscess in 35%, localized peritonitis in 16%, fistula formation in 14%, colonic obstruction in 12% and intramural sinus tracts in 9% [17].

The organisms isolated in this case were predominantly Streptococcus milleri. There is no indication within the current literature of this organism's potential for gas formation. Mixed coliforms and anaerobes were also grown; these are gas forming and are commonly found within the large bowel. Streptococcus milleri are strongly associated with pyogenic infections and abscess formation throughout the body [18] and are known to be the most commonly isolated bacteria from intracranial abscesses [19]. Although they are known to cause cerebral abscesses and bacterial meningitis [20], our patient did not demonstrate features of abscess formation clinically or radiologically and was not severely compromised systemically.

We postulate that the air seen within the ventricles arose via the fistulae as seen intraoperatively. This may then have reached the spinal canal (as demonstrated by the presence of gas at multiple levels in the spinal canal) either via a breach in the dural nerve sheath of the sacral nerve plexus or via the pre-sacral venous plexuses. In the case of the former, a breach in the dural nerve sheath would result in passage of gas into the subarachnoid space, and this has indeed been described as a complication of metastases from a rectal adenocarcinoma with adjacent bone erosion [21]. The second potential route of gas entry would be via the pre-sacral venous plexuses, which drain into the intervertebral veins accompanying the spinal nerves through the intervertebral foramina. These veins drain the veins of the spinal cord and the internal and external vertebral venous plexuses. Batson demonstrated that these veins lack effective valves and can thus allow blood backflow (and in this case also gas), particularly if there is either elevated intra-abdominal pressure or postural alteration [22–24]. In our case, pressure changes in venous flow may have occurred because of the presence of the pre-sacral abscess. This may have resulted in backflow of gas, ultimately to the internal vertebral venous plexus and from there into the subarachnoid space.


   Conclusions
Top
 Abstract
 Case report
 Discussion
 Conclusions
References
 
Pneumocephalus is a well-documented radiological finding, and many aetiological causes have been described. This is the first report of diverticulitis as a cause for pneumocephalus. The organisms isolated from the blood cultures (Streptococcus milleri) are known to cause suppurative cerebral disease. They are not typically gas forming. We therefore hypothesize that gas from the pre-sacral diverticular abscess reached the cerebral ventricular system via the spine, either due to a breach in the spinal dural nerve sheaths or via the spinal venous plexus.

Received for publication March 30, 2006. Revision received September 13, 2006. Accepted for publication September 15, 2006.


   References
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 Abstract
 Case report
 Discussion
 Conclusions
 References
 

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