Acute bacterial meningitis or ventriculitis after the transsphenoidal (TS) surgery infrequently leads to a potentially fatal situation of intraoperative cerebrospinal fluid (CSF) leakage [1] [2] . Although Pseudomonas aeruginosa (P. aeruginosa), one of the gram-negative rods, is common in the nasal cavity, it rarely causes postoperative intracranial infections. However, development of a P. aeruginosa infection in the central nervous system (CNS) can lead to serious meningitis or ventriculitis [3] . Therefore, the treatment of P. aeruginosa infection requires prompt medical evaluation and appropriate antibiotic selection [4] .

CSF leakage associated with the spread of endoscopic procedures has caused an increase in the risk of postoperative meningitis and ventriculitis, if the skull base construction could not be performed successfully. Hydrocephalus, of either the communicating or the obstructive type, is occasionally found in patients with meningitis or ventriculitis [5] [6] . We present here a very rare case of obstructive hydrocephalus caused by P. aeruginosa infection following TS surgery.

A 36-year-old man presented with disturbances of consciousness due to panhypopituitarism was transferred to our hospital. He had no obvious past medical history. Hormone replacement was immediately initiated with hydrocortisone and thyroxin. Magnetic resonance imaging (MRI) showed a huge cystic tumor extending from the intra-sellar region into the frontal lobe (Figure 1(a)). Although most of the tumor was removed via trans-ven- tricular approach, the residual intrasellar portion and a direct passage from the intrasellar region to the right lateral ventricle were detected on postoperative MRI (Figure 1(b)).

TS surgery for the residual intra-sellar lesion was planned. During the endoscopic endonasal TS surgery, a small amount of pus was found adjacent to the sella turcica at the sphenoid sinus, which was found on pre-oper- ative MRI retrospectively (Figure 2(a) and Figure 2(b)). After aspiration and saline irrigation of the pus, the calcified intrasellar lesion was entirely removed, allowing CSF leakage from right lateral ventricle (Figure 2(c)). Sellar floor plasty was successfully performed by placing the fat graft in the sella, the fascia in the subdural space and the nasal pedicled mucosal flap over the sella floor. Cefazolin was administered according to the first line of postoperative antibiotics protocol determined by hospital infection control team in our hospital.

The patient suffered from high-grade fever and headache immediately after the operation. The number of white blood cells in CSF was elevated to 5300/μL, and sugar was decreased to 5 mg/dL, indicating severe bacterial meningitis. The antibiotic was changed from cefazolin to ceftriaxone without achieving remarkable improvement. Then, culture of the pus in the sphenoid sinus demonstrated to be negative, possibly because the sample was picked up after the saline irrigation. P. aeruginosa was detected on the CSF culture as the responsible pathogen and found to be sensitive to meropenem, which did not resolve the CSF findings in two weeks. Although P. aeruginosa also was sensitive to ceftazidime and relieved the infectious activity initially, the meningitis relapsed.

Shortly, he developed consciousness disturbance and a computed tomography (CT) scan showed remarkable whole ventriculomegaly (Figure 3(a)). External ventricular drainage was then placed, after which he recovered immediately. Because this pathophysiology was diagnosed as ventriculitis due to P. aeruginosa, removal of the infected fascia and fat graft in the sellar turcica and sellar floor reconstruction were performed. After these procedures, high-grade fever and headache could be controlled.

The intra-ventricular administration of a contrast agent clearly revealed an occlusion of the fourth ventricle outlet, suggesting this was the cause of obstructive hydrocephalus (Figure 3(b)). Endoscopic third ventriculostomy (ETV) was successfully performed. Endoscopic intraoperative views showed many pigmented spots on the ventricular wall, suggesting remnant of ventriculitis (Figure 3(c)). Ceftazidime could be ceased a week after ETV. The patient could discharge from hospital. He has been free from ventriculitis for four years, and hormone replacement has been maintained with hydrocortisone and thyroxin all the time.

Meningitis and ventriculitis are major complications following TS surgery [7] [8] , and the rates of their incidence are reported to be 0.3% - 3.3% [9] - [11] . There are some evidences that the use of prophylactic antibiotics may increase the incidence of infection with gram-negative organism among patients with CSF leaks [2] . The gram-negative bacilli were reported to be isolated from 80% of patients with hospital-acquired meningitis and most of them were received prophylactic antibiotics [12] . The hospitalization and the prophylactic use of antibiotics alter host flora and allow for meningitis with opportunistic gram-negative rods in patients with CSF leaks [2] . P. aeruginosa is a causative pathogen with low incidence among postoperative meningitis following TS surgeries, early detection of P. aeruginosa meningitis is mandatory for successful treatment [1] [2] . We believed that one successful method for early detection of P. aeruginosa is to perform a culture of the nasal cavity prior to irrigation with saline during TS surgery.

In our case, progressive consciousness disturbance, prompt recovery from consciousness disturbance with external ventricular drainage, and remarkable whole ventriclomegaly indicated occlusion of the foramen of Luschka and Magendie. In patients with complications of ventriculitis and intracranial hypertension, the presence of obstructive hydrocephalus should be strongly suspected. Once a diagnosis of the fourth ventricle outlet occlusion is made, ETV is the first choice of the treatment to ensure a good outcome [13] [14] .

Several possible mechanisms have been postulated for hydrocephalus associated with bacterial ventriculitis, such as the blockage of the CSF flow owing to leptomeningeal inflammation or obliteration of the subarachnoid space and the foramen of Luschka and Magendie due to the presence of meningeal exudates [5] [6] . In cases of obstructive hydrocephalus, CSF flow is blocked at the third or fourth ventricle. The fulminant course of P. aeruginosa ventriculitis may present as acute obstructive hydrocephalus [3] .

Sharma reported factors predicting the development of postoperative hydrocephalus following TS surgery. These factors included age, intraoperative and postoperative CSF leakage, CSF infection, and duration of hospital stay [15] . In our patient, intraoperative CSF leakage was encountered but postoperative CSF leakage could not be found, suggesting that the residual sphenoid sinusitis near the sellar floor directly connected to the tumor cavity and right lateral ventricle (Figure 4). Because our sellar floor plasty―placement of the fascia in the subdural space―may allow CSF to travel between the tumor cavity and the residual sinusitis, epidural autologous bone and/or fascia placement should be added to prevent postoperative P. aeruginosa infection.

Meningitis is one of the major complications following TS surgery, and its rate of occurrence is increased if cerebrospinal fluid leakage develops postoperatively. If the Pseudomonas aeruginosa infection occurs in a compromised host, such as in patients with panhypopituitarism, a potential diagnosis of progressive obstructive hydrocephalus should be considered based on the clinical status and neuroradiological evaluation, and prompt surgical intervention should be applied to prevent neurological deterioration.

The authors declare that they have no conflict of interest.

CNS: central nervous system

CSF: cerebrospinal fluid

CT: computed tomography

ETV: endoscopic third ventriculostomy

MRI: magnetic resonance imaging

P. aeruginosa: Pseudomonas aeruginosa