====== Postoperative pneumocephalus ======

===== Etiology =====

● [[Craniotomy]]: risk is higher when patient is operated with surgery in the [[sitting position]]
((Lunsford LD, Maroon JC, Sheptak PE, et al. Subdural Tension Pneumocephalus: Report of Two Cases. J Neurosurg. 1979; 50:525–527))

● shunt insertion
((Little JR, MacCarty CS. Tension Pneumocephalus After Insertion of Ventriculoperitoneal Shunt for Aqueductal Stenosis: Case Report. J Neurosurg. 1976; 44:383–385))
((Pitts LH, Wilson CB, Dedo HH, et al. Pneumocephalus Following Ventriculoperitoneal Shunt: Case Report. J Neurosurg. 1975; 43:631–633)).

● [[burr hole]] [[drainage]] of [[chronic subdural hematoma]]
((Caron J-L, Worthington C, Bertrand G. Tension Pneumocephalus After Evacuation of Chronic Subdural Hematoma and Subsequent Treatment with Continuous Lumbar Subarachnoid Infusion and Craniostomy Drainage. Neurosurgery. 1985; 16:107–110))
((Ishiwata Y, Fujitsu K, Sekino T, et al. Subdural Tension Pneumocephalus Following Surgery for Chronic Subdural Hematoma. J Neurosurg. 1988; 68:58–61)): 
incidence is probably < 2.5%
((Ishiwata Y, Fujitsu K, Sekino T, et al. Subdural Tension Pneumocephalus Following Surgery for Chronic Subdural Hematoma. J Neurosurg. 1988; 68:58–61))
although higher rates have been reported.

[[Ventriculostomy]].
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Common causes of postoperative [[pneumocephalus]] are [[intracranial surgery]] or [[spinal surgery]] as well as some ENT operations, such as paranasal sinus surgery, nasal septum resection, or nasal polypectomy
((Solomiichuk VO, Lebed VO, Drizhdov KI. Posttraumatic delayed subdural tension pneumocephalus. Surg Neurol Int. 2013;4:37.)).
In some cases, the incidence after supratentorial craniotomy has been reported to be 100%. Sixty-six percent of these PNC were judged to be moderate or large, and the incidence decreased to 75% by postoperative day 7. Nonetheless, 11.8% of the scans obtained during the 2nd postoperative week had PNC that were judged to be moderate or large
((Reasoner DK, Todd MM, Scamman FL, Warner DS. The incidence of pneumocephalus after supratentorial craniotomy. Observations on the disappearance of intracranial air. Anesthesiology. 1994;80:1008–12.)).

==== Pneumocephalus after Nitrous oxide ====

[[Pneumocephalus after Nitrous oxide]].

==== Pneumocephalus after Deep Brain Stimulation ====

[[Pneumocephalus after Deep Brain Stimulation]].

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Contributing factors have been implicated in the pathogenesis, including [[nitrous oxide]] anesthesia, duration of surgery, [[hydrocephalus]], a functional [[ventriculoperitoneal shunt]], intraoperative administration of [[mannitol]], head position, duration of surgery,  [[hydrocephalus]], [[hyperventilation]], spinal anesthesia, barotauma, continuous CSF drainage via [[lumbar drain]], epidural anesthesia, infections, and neoplasms
((Satapathy GC, Dash HH. Tension pneumocephalus after neurosurgery in the supine position. Br J Anaesth. 2000;84:115–7.)).

The risk of pneumocephalus following craniofacial procedures is significant, and may be increased by the use of lumbar drainage of CSF intraoperatively. 

see [[Pneumocephalus in the sitting position]].

see [[Tension pneumocephalus after chronic subdural hematoma evacuation]].

===Posterior fossa surgery===

[[Postoperative pneumocephalus after posterior fossa surgery]].

===Endoscopic endonasal skull base surgery===
Postoperative pneumocephalus is a common occurrence after endoscopic endonasal skull base surgery (ESBS). The risk of cerebrospinal fluid (CSF) leaks can be high and the presence of postoperative pneumocephalus associated with serosanguineous nasal drainage may raise suspicion for a CSF leak. 

Postoperative pneumocephalus is much more common following extended approaches than following transsellar surgery. Merely the presence of pneumocephalus, particularly in the frontal or intraventricular locations, is not necessarily associated with a postoperative CSF leak. A "suspicious" pattern of air, namely pneumocephalus in the convexity, interhemispheric fissure, sella, parasellar, or perimesencephalic locations, is significantly associated with a postoperative CSF leak. The presence and the score of "suspicious" pneumocephalus on postoperative imaging, in conjunction with the learning curve and the type of endoscopic approach, provide the best predictive model for postoperative CSF leaks
(({{pubmed>long:24995788}}))

===== Complications =====
Postoperative pneumocephalus is associated with a higher risk of [[chronic subdural hematoma recurrence]]