Abstract
This case illustrates the need to consider pneumocephalus (intracranial air) in the differential when cognitive changes develop following spinal surgery.
Lumbar decompression for acute and chronic degenerative spinal pathology is one of the most common procedures performed by spinal surgeons, neurosurgeons and some orthopaedic surgeons. It is associated with several recognized complications, however, the presence of intracranial air (pneumocephalus) postoperatively is generally not a recognized feature.
To the authors' knowledge there have been no previous reports of pneumocephalus arising secondary to lumbar decompression.
A 63-year-old woman with a background of chronic degenerative lumbar spinal stenosis presented as an elective for re-do L3, L4 and L5 decompression. The MRI scan of her lumbo-sacral spine revealed posterior disc protrusions at L3/4 and L4/5 levels.
She underwent revision laminectomy, performed at L3/4 and L4/5 to decompress the lateral recesses at these levels. Adequate decompression was performed; however, it was noted that dural leak had occurred, this was sealed with a 3.0 prolene stitch, duragen and tisseal application. The tissues closed in layers and staples applied to the skin.
For cerebrospinal fluid (CSF) leak the patient was managed with strict, flat bed rest for 48 hours postoperatively.
Less than 24 hours postoperatively, it was noticed that she had become confused, restless, disoriented and complaining of headache. She was mildly febrile, with a temperature of 37.9°C. Her physical examination was unremarkable.
A CT head scan performed the same day ( Figure 1) showed pneumocephalus, the presence of air within the cisterns and the ventricular system.
To hasten recovery, she was administered with high flow oxygen at a rate of 10 L per minute, and by 5 days the confusion had settled, with complete resolution of the intracranial air on repeat CT imaging.
Introduction
Lumbar decompression for acute and chronic degenerative spinal pathology is one of the most common procedures performed by spinal surgeons, neurosurgeons and some orthopaedic surgeons. It is associated with several recognized complications, however, the presence of intracranial air (pneumocephalus) postoperatively is generally not a recognized feature.
To the authors' knowledge there have been no previous reports of pneumocephalus arising secondary to lumbar decompression.
Case report
A 63-year-old woman with a background of chronic degenerative lumbar spinal stenosis presented as an elective for re-do L3, L4 and L5 decompression. The MRI scan of her lumbo-sacral spine revealed posterior disc protrusions at L3/4 and L4/5 levels.
She underwent revision laminectomy, performed at L3/4 and L4/5 to decompress the lateral recesses at these levels. Adequate decompression was performed; however, it was noted that dural leak had occurred, this was sealed with a 3.0 prolene stitch, duragen and tisseal application. The tissues closed in layers and staples applied to the skin.
For cerebrospinal fluid (CSF) leak the patient was managed with strict, flat bed rest for 48 hours postoperatively.
Less than 24 hours postoperatively, it was noticed that she had become confused, restless, disoriented and complaining of headache. She was mildly febrile, with a temperature of 37.9°C. Her physical examination was unremarkable.
A CT head scan performed the same day ( Figure 1 ) showed pneumocephalus, the presence of air within the cisterns and the ventricular system.
To hasten recovery, she was administered with high flow oxygen at a rate of 10 L per minute, and by 5 days the confusion had settled, with complete resolution of the intracranial air on repeat CT imaging.
Discussion
Pneumocephalus is commonly seen in clinical practice ( Table 1 ). Typical neurosurgical causes include trauma, infection and tumour, particularly those tumours eroding the skull base in the anterior cranial fossa. 1 Pneumocephalus may also occur iatrogenically at the time of intracranial surgery. It is not pathological and may be seen routinely on postoperative neuro-imaging. Pneumocephalus is rarely encountered in the absence of the aforementioned entities. 2 There are various examples of some uncommon causes of this condition. These include: spontaneous pneumocephalus associated with recurrent colorectal carcinoma. 3 Here the most likely cause described is a fistulous tract developing between the recurrent gastrointestinal tumour and a sacral nerve root. Another remarkably rare cause has been reported as a complication of diverticulitis, 4 presumably by a similar portal of entry into the cranial cavity. Pneumocephalus has also occurred as a complication of lumbar punctures, and after lumbar epidural steroid injection. 5 Factors which have been implicated in the formation of postoperative pneumocephalus include upright position (surgery for posterior fossa tumours or pineal tumours), factors decreasing the brain volume such as surgical decompression, intracranial dehydration, hyperventilation, and use of nitrous oxide during surgery. 6 Pneumocephalus is a well-known complication of spinal and epidural anaesthesia, but is extremely rare after diagnostic or therapeutic lumbar puncture. 7 Possible complications that can occur as a result of lumbar decompression include dural tear with associated CSF leak, retroperitoneal and nerve root injury, pseudoarthrosis, infection, instability and nerve root damage. Pneumocephalus is not regarded as a recognized complication of this procedure. It is likely, therefore, that the presence of a dural tear provides a ball-valve mechanism for the potential route of air entry by the creation of a negative pressure which can draw air into and through the spinal canal, and hence into the cranial cavity through the foramen magnum, but does not allow air to exit. Hence, both a defect in the dura and reduction in intracranial pressure, caused by CSF leakage contribute to pneumocephalus formation.
Tension pneumocephalus is the term for intracranial air which causes mass effect and abnormal neurological signs. It mimics an expanding intracranial space-occupying lesion and may lead to rapid deterioration. Symptoms include headache, restlessness, confusion and disorientation. In our patient the initial postoperative CT head scan confirmed pneumocephalus, though no obvious mass effect was seen, this may well have been present in the recovery room, immediately postoperatively initiating headache and confusion.
We have also considered other possible causes for the development of confusion following spinal surgery. Studies have shown that this is likely to be multifactorial. Risk factors implicated appear to include an increased intake of oral medication including high-dose steroids, poor ambulation, namely admission on a stretcher or in a wheelchair. Age also appears to be a contributory factor, with patients in their 70s and above, along with those with hearing impairment asimmons@example.com. 8 These factors tend to point to a poorer preoperative physical condition. Studies have also shown that a low haematocrit and haemoglobin concentrations in the first couple of days post-spinal surgery are implicated in confusion post-spinal surgery. 9 Pneumocephalus may manifest symptoms and signs ranging from a persistent headache, lethargy and confusion to hemiparesis and hemiplegia. It has been proposed that the rate of pneumocephalus resolution following craniotomy (arguably the most likely iatrogenic aetiology) at room air (21% FiO 2 ) is 31% per 24 hours. A non-rebreather mask used to deliver 68% FiO 2 results in a mean rate of resolution of pneumocephalus of 65% per 24 hours. 10 Strategies employed to treat pneumocephalus involve nursing a patient in the vertical position. If the patient remains symptomatic it may become necessary to repair the bony and dural defect and if indicated placement of a drain into the air cavity. No craniotomy had been performed in our patient, but the rationale for treatment remained the same. Here, the added concern was the presence of CSF leak from dural tear, hence, we decided to gradually sit the patient up after 48 hours postoperatively.
Our patient was known to be diabetic, this combined with symptoms of headache and confusion postoperatively, can be assumed to have put her at a higher risk of developing an infection. However, this is less common in the immediate postoperative period. It was only due to the search for a possible non-surgical cause for her symptoms that CT head imaging was performed, revealing the presence of pneumocephalus.
Conclusion
Pneumocephalus should be considered as part of the differential diagnosis in patients who have had a dural puncture during spinal procedures and who present postoperatively with unexplained headaches and cognitive changes. The appropriate investigation would be a plain CT head scan, and where confirmed the pneumocephalus treated with supplemental high-flow oxygen therapy.

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