Symptomatic Compressive Pneumocephalus: Rare Complication of Posterior Spine Surgery

Pneumocephalus is the presence of air intracranially, this pathology is mostly seen in traumatic injury, however it remained exceptional in posterior spine surgery. In this study, we report a clinical case of a 66 years old woman who was operated for lumber spinal stenosis with spondylolisthesis presented a drowsiness, CT scan showed a compressive pneumocephalus (mount fuji sign) and pneumorrachis. A conservative treatment has been set up. The evolution was marked by improving its state of consciousness, the patient was discharged on day 10 post operatively with a brain CT that showed regression of PC.


Introduction
Pneumocephalus (PC) is defined as the presence of air intracranially. This condition is seen frequently in the cranio-facial trauma, surgery of brain tumor or infectious lesions. The PC can be epidural, subdural, intraparenchymal or intraventricular. The PC after a spine surgery is a rare complication that must systematically lead to look for a breach of the dura mater. Most often we find a pneumorachis, which is usually asymptomatic, confirms the origin of this complication. We describe below the case of a patient who was treated in our department of Neurosurgery of CHU Hassan II of Fez who presented a PC after posterior spine surgery.

Clinical Case
Woman 66 years old, with past medical history of hypertension on treatment for 4 years. She has one-year history of back pain with intermittent claudication. On examination a lumbar spinal pain syndrome without associated neurological signs was found.

Pneumocephalus (PC) is defined as the presence of air
intracranially whose location can be extra-axial or intra-axial [1]. According to Markham, PC in 74% is due to a trauma, 24% to an infectious cause, and 9% following surgery of the skull [2].
The PC can also be observed following a lumbar puncture or as a rare complication of spinal anesthesia [3,4]. The PC is due to two mechanisms: 'the inverted soda bottle mechanism' and ' the ball valve mechanism'. The inverted soda bottle: the flow of CSF due to a breach of the dura mater, will generate negative intracranial pressure, therefore, the air will penetrate in to replace intracranial CSF to have a normal intracranial pressure. [2,5,6].
The ball valve mechanism: the pressure gradient increases and will form a large air collection intracranially [5][6][7], this pressure gradient is formed when the pressure exceeds the pressure extracranially, and intracranial presence of a dural tear. This gradient increase will generate an increase in pressure of paranasal cavities that will push the air through intracranial dural tears [5,6,8]. The leaving of a redon drain predisposes the patient to a PC in the presence of a CSF leak [9]. Ayberk et al. reported a case of spontaneous PC without breach on the dura mater, they then concluded that the increase in intra-abdominal pressure due to the position is the cause of this PC [10].
In the review of the literature made by Gauthé R. et al. About spontaneous pneumocephalus after spine surgery, eight cases have been published and iatrogenic breach was noted in six cases [11].
The presentation is not specific, the PC can then be asymptomatic Nowak et al reported a case of PC associated with acute subdural hematoma [12]. Apart from this case, the authors instead opt for conservative treatment.
Spontaneous resorption of the PC may be seen in 85% of patients between 2-3 weeks, during which prophylactic treatment of meningitis can be considered in case of CSF leak [9].

Conclusion
The PC is a rare complication in posterior spine surgery, the clinical picture is variable and nonspecific. The realization of a brain CT scan is compulsory in every patient with neurological symptoms postoperatively. The conservative approach may be sufficient even in the presence of severe neurological signs.