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The enigma of pituitary abscess

Jain KC, Varma A, Mahapatra AK. (Department of Neurosurgery,Neurosciences Centre, All India Institute of Medical Sciences,New Delhi, India.) Pituitary abscess: A series of six cases. Br JNeurosurg 1997;11:139-43.

SUMMARYOf the 1000 patients with pituitary masses operated upon at the AllIndia Institute of Medical Sciences in the past decade, 6 had pituitaryabscess-an incidence of 0.6%. In a rare disease where most reportsare of isolated cases, this Indian series is comparatively large. Therewere 3 females and 3 males-an adolescent and 5 adults aged be-tween 17 and 42 years. They all presented with deteriorating visionandvisual defects, 4 had raised intracranial pressure and the 3 womenhad amenorrhoea. Four of the 6 patients had a normal hormonalprofile. The computed tomography (CT) scan of 5 patients showedsellar and suprasellar isodense ring enhancing lesions; one patienthad magnetic resonance imaging (MRI). In spite of the suggestiveclinical characteristics, adequate neuroradiological and biochemicalinvestigations, the authors diagnosed pituitary abscess preoperativelyin only 1 of the 6 cases.

The abscess was accessed and drained through frontal craniotomyin 2 cases and by microsurgical trans-sphenoidal approach in 4 cases.There was no mortality in this series but in 3 patients the abscessrecurred 18 months, 3 years and 8 years after the initial drainage.These were dealt through a frontal craniotomy.

One abscess had occurred postoperatively after craniotomy forpituitary adenoma; the organisms responsible were Klebsiella sp andProteus. The other five, presumably primary abscesses, were associ-ated with aspergillus in 2 cases, mycobacterium in 1and were sterilein 2. Two of the primary abscesses were associated with otherpituitary pathologies-acromegaly and Rathke's pouch cyst.

COMMENTFirst described by Simmonds in 1914,1 pituitary abscess hasremained a rare and puzzling clinicopathological entity. Mostaccounts in the literature are isolated case reports, with a fewpapers such as this one containing more than one case. Reportshave come from the United Kingdom.>" France.t" Germany.v'"Spain," Italy ,12Belgium,'? Poland," the United States,":" SouthAfrica,2l)·21Ivory Coast in West Africa," Turkey," Japan24-27andChina. 21.29

The equal male-to-female distribution reported in this paper isat variance with the literature which shows that primary pituitaryabscess occurs predominantly in women.5.20The statement thatthe disease occurs in various age groups needs modification. It ismore correct that pituitary abscess is predominantly a disease ofadults and is rare in children. One of the 5 patients in the Durbanseries was aged 13 years20and Schwartz et al. 17encountered thecondition in an adolescent girl.

About 100 patients with pituitary abscess have been describedin the literature." Grosskopf et al.' reviewed 3I cases reportedduring 1970-85; ten years later, the documented cases had risento 80,25indicating the increased awareness ofthe disease and theimpact of newer neuroradiological techniques in its diagnosis.

Nevertheless, the disease remains comparatively rare. In thispaper from India, pituitary abscess accounted for less than I % ofabout 1000 pituitary lesions treated. A series of 111 pituitarylesions, treated by trans-sphenoidal hypophysectomy in New

THE NATIONAL MEDICAL JOURNAL OF INDIA VOL. 10, No.5, 1997

York, had only I case of pituitary abscess.'? In a hospital fromTaiwan, there was only 1 case among 205 treated pituitarylesions."

The preoperative diagnosis of pituitary abscess remains diffi-cult even with the new imaging techniques of CT and MRI.7.21Inthis paper, the authors made a preoperative diagnosis in only 1 oftheir 6 patients. The clinical features they described are the resultof pressure on the visual pathway and pituitary dysfunction.These features have some limitations in assisting a preoperativediagnosis. Firstly, they can be produced by other pituitary masses,such as an adenoma and craniopharyn gioma. Secondly, the so-called characteristic clinical features of puuitary abscess are notuniformly present. For instance, all the 3 women with pituitaryabscess in the study by Ahmed et aI.5 had amenorrhoea but nonehad visual disturbance. Thirdly, systemic effects of the infectionare usually not present to evoke the suspicion of an infectivespace-occupying lesion of the sella turcica.16.27Two of the 6patients in this series' had systemic infection. Only one of the 5patients in the Durban series was sick on presentation."

Computed tomography and MRI are helpful in diagnosingsellar and parasellar lesions. Although not pathognomonic, CTand MRI findings which are highly suggestive of pituitary abscesshave been described. 3.5CT shows a slightly low density suprasellarexpanding mass lesion with an enhanced thin wall and MRI showshyperintensity on T1 weighted images and hypo-intensity with aperipheral ring form on T2 weighted images." The MRI intensityof the central area of the abscess depends on the amount of blood,and the quantity of protein and water in the lesion. 13.29

Endocrine dysfunction is more frequent in these patients thanwas previously reported." Ahmed et al? pointed out the impor-tance of preoperative and postoperative endocrine assessments inthe diagnosis and management of pituitary abscess.

Since the clinical and neuroradiological features of pituitaryabscess may be indistinguishable from those of a pituitary tumour,the diagnosis is made with certainty at surgery. 21The method ofchoice is drainage by the trans-sphenoidal route, and not frontalcraniotomy as the latter increases the risk of spilling the infectioninto the cerebrospinal fluid.26Early evacuation of pus through thetrans-sphenoidal route, along with appropriate antibiotic therapyand steroids have dramatically reduced the mortality from about60%30to nil in this series and the Durban study.?" The results ofsurgery are good with most patients recovering vision and men-struation becoming normal."

However, the morbidity can be high. Aseptic meningitis canoccur and may be recurrent. In the study by Landers et al.;" 2 ofthe 5 patients developed this complication. Hypopituitarism is athreat and may require hormone replacement. 25Recurrence of theabscess is a major concern as shown in this series. A long followup is necessary since recurrence can occur many years later.

Surgery is the best treatment for pituitary abscess-it confirmsthe diagnosis and evacuates the pus. Nevertheless, medical treat-ment alone has been used either because of the lack of facilities foroperation or the patient being too ill for surgery. A course ofcefotaxime and metronidazole for one month and netilmicin fortwo weeks controlled the systemic infection in one patient in theIvory Coast report. The medication cured the visual disorder andled to a reduction in the size of the gland on follow up CT scan."

Bacteriological study of the abscess has produced variableresults. Two of the 6 patients in this series had sterile abscesseswhich were present in all the 5 cases in the Durban series. Twoimmunocompetent patients in this series had aspergillus abscesswhich is very rare.":"

SELECTED SUMMARIES

Another puzzle is the unclear aetiology of most pituitaryabscesses. It has occurred in association with meningitisv" andthrombophlebitis of the cavernous sinus." However, in about50% the pathogenesis cannot be explained' but some predispos-ing factors have been identified. These include sphenoidal sinusinfection-" hypogammaglobunaemia' hyperglycaemia and im-munosuppression."

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ADELOLA ADELOYEDepartment of Surgery

College of MedicineUniversity of Malawi

BlantyreMalawi