SKULL BASE SURGERYNOLUME 4, NUMBER 3 JULY 1994

CASE REPORT

Temporary Unilateral Amaurosiswith Pneumosinus Dilatans

of the Sphenoid SinusEdgar Bachor, M.D., Rainer Weber, M.D.,

Gabriele Kahle, M.D.,and Wolfgang Draf, M.D., F.R.C.S.

Pneumosinus dilatans (PSD) is an abnormal dilatationof an otherwise normal paranasal sinus. This finding was

first reported by Meyes in 1898' and classified by Benjaminsin 1918.2 Lombardi et al reviewed all patients with this rare

abnormality and characterized its common features in 1968.3Although the etiology of a PSD is not known, it has beendescribed in association with many disorders: fibrous os-

seous dysplasia,4.5 brain anomalies such as hydrocephalus6and arachnoid cysts,7-9 Klippel-Trenaunay (angio-osteo-hypertrophy),10 and Melnick-Needles syndrome (osteo-dysplasia-syndrome).l' Several reports have postulatedthat a sphenoid PSD may be the first sign of a meningiomaat the tuberculum sellae or the planum sphenoidale.12-18

Clinically, a PSD can present with a variety of signsand symptoms ranging from facial swelling, especially

with frontal and maxillary sinus dilatation, to headaches or

vertigo. Increasing loss of vision and reduction of visualfields is frequently found in association with PSD andmeningiomas. 12-18 In massive dilatation of the sinuses,proptosis'9 or exophthalmus may be seen. 19,20 If the hypo-physis is compressed, there can be signs of endocrinedisturbance.3"9 Pneumosinus dilatans may be found acci-dentally in asymptomatic individuals.21,22

Benjamins2 distinguished PSD from sinus pneumo-

cele; he defined the latter as an enlarged sinus with a defectin the bony wall. Pneumoceles are most common in themaxillary sinus.23-35

We report on the rare case of a patient with suddenreversible unilateral loss ofvision and PSD of the sphenoidsinus of unknown etiology.

169

Skull Base Surgery, Volume 4, Number 3, July 1994 Department of Otolaryngology, Head, Neck and Facial Plastic Surgery, CommunicationDisorders (E.B., R.W, WD.) and Department of Radiology (G.K.), Stiidtisches Klinikum Fulda, Fulda, Germany Presented at the First Congressof the European Skull Base Society, Riva del Garda, Italy, September 26-30, 1993 Reprint requests: Dr. Bachor, Department of Otolaryngology,Universitit Regensburg, Franz-Joseph-StrauB Allee 11, 93042 Regensburg, Germany Copyright © 1994 by Thieme Medical Publishers, Inc., 381Park Avenue South, New York, NY 10016. All rights reserved.

SKULL BASE SURGERYNOLUME 4, NUMBER 3 JULY 1994

CASE REPORT

WJ. is a 37-year-old truck mechanic who experi-enced sudden blindness in the left eye and frontal head-ache in September 1990 while mountain climbing above3000 m. Vision recovered completely after descendingbelow 2000 m. An ophthalmological examination on thesame day demonstrated no abnormality. A second climb-ing expedition again resulted in sudden loss of vision. Asecond ophthalmological and a neurological examinationrevealed no reason for the origin of the patient's com-plaints. A visit to an otolaryngologist demonstrated anormal examination except for a septal deviation. W.J. wasreferred to our department and a high resolution axialcomputed tomogram of the paranasal sinuses showed aPSD of the sphenoid sinus with a dehiscent optic canal(Fig. 1). Believing that the optic nerve was being com-pressed, we performed an endonasal microendoscopicresection36 of the anterior wall of the left sphenoid sinus

combined with a septoplasty under general anesthesia.During surgery the left aspect of the sphenoid sinus wasexplored and found to be air filled, and an area of absentbone could be identified. We discharged WJ. after anuncomplicated postoperative course of 7 days. At an am-bulatory follow-up 2 years later the patient reported nosymptoms while climbing above 300 m. Postoperativeendoscopy showed a wide open, air filled sphenoid sinus.Vision was normal.

MATERIALS AND METHODS

We reviewed the literature from 1969 to 1992 usingMedline. Pneumosinus dilatans and pneumocele wereused as keywords. Additional articles were selected fromreferences of the pertinent literature. A total of47 articleswere found, of which 3 were eliminated due to insufficientpatient information (age, sex, location, etc) or becausethey were unnotable. We also eliminated publications in

Figure 1. Preoperative axialhigh resolution computerized to-mograms of the paranasal sinuses ofthe patient W.J. A: Section below theoptic canal showing the pneumo-sinus dilatans of the sphenoid sinus.B: Section at the level of the opticcanal. The optic nerve is seen with-out bony cover in the sphenoid sinus(arrow).170

PNEUMOSINUS DILATANS-BACHOR ET AL

which the same patients were reported on repeatedly.Thirty-eight publications remained, with a total of 75patients (Table 1).

In reviewing the literature there seemed to be a differ-ence between a pneumocele, which has a trap-valve mech-anism and occurs more suddenly, and a PSD, which usu-

ally has a much longer history. Since the origin ofa PSD isunknown and the distinction between a PSD and a pneu-

mocele by a bony defect is very convenient, we decided to

use the original classification by Benjamins2 and Jeans20to select cases of idiopathic PSD and pneumocele.

RESU LTS

The literature review revealed 24 cases of an idio-pathic PSD (Table 2). The frontal sinus was most affected

Table 1.

Authors YearBenedikt et al

1991Borelli et al1979

Bourdial1970

Candan et al1990

Chan et al1992

Dhillon et al1987

Dross et al1992

Gray et al1978

Hirst et al1979/82

Jarvis 1974

Komori et al1988

Legent 1991

Leonardi et al1976

Lloyd 1985

Macialowicz1969

Meyer-Breiting1978

Overview of Literature from 1969 to 1992 with Pneumocele and Pneumosinus Dilatans (PSD)Bony Defect

Type Sex Age Location (Yes/No) Symptoms OriginPSD F 17 Ant.ethm L Y Nasal congestion, Spont. drainage

PSD

PSDPSDPSDPSD

PneumocelePneumocele

PSD

PSD

PSD

Pneumocele*

PSDPSDPSD

Pneumocele

PSD

PSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSDPSD

M 18 Sphenoid

M 45 Frontalis RM 20 Frontalis LF 70 Frontalis LM 17 Frontalis R

M

M

F

335116

NotNotNot

Maxillar RMaxillar RMaxillar L+R

F 35 Sphenoid L

M 37 Sphenoid L

F 44 Frontal L

M 18 SphenoidM 35 SphenoidF 14 SphenoidM 18 Sphenoid,

frontal RF 36 Maxillar R

M

M

M

M

M

FFFFF

FFM

FF

F

F

2316134766664022523565192415172128

Frontal RFrontal LMaxillar RSphenoidSphenoidSphenoidSphenoidSphenoidSphenoidSphenoidSphenoidAnt ethmoidAnt ethmoidAnt ethmoidMaxillar L+RMaxillar L+REthmoid

PSD F 76 Posteriorethmoid

SphenoidPneumocele M 47 Ethmoid R

painN Asymptomatic,

epilepsyknown Rhinitisknown Swellingknown MeningitisN Swelling, pain

Y Numbness, swellingY SwellingN Proptosis, loss of

visionN Headaches, blurred

visionN Asymptomatic

Y Proptosis, pain

NNNy

Loss of visionLoss of visionLoss of visionProptosis, pain

N Swelling

Not knownNot knownNot knownNot knownNot knownNot knownNot knownNot knownNot knownNot knownNot known

NNNNNN

SwellingSwellingProptosisLoss of visionLoss of visionLoss of visionLoss of visionLoss of visionLoss of visionLoss of visionHemiplegiaProptosisProptosisProptosisProptosisExopthalmusProptosis

N Loss of visionY Chronic sinusitis

Double vision

of mucoceleIdiopathic

IdiopathicIdiopathicIdiopathicValve

ValveValve, radiationFibro-osseous

diseaseArachnoid cyst

Arachnoid cyst,adenoid CA

Valve

MeningiomaMeningiomaMeningiomaMucocele

Idiopathic

IdiopathicIdiopathicIdiopathicMeningiomaMeningiomaMeningiomaMeningiomaMeningiomaMeningiomaMeningiomaMeningiomaFibrous osseus

diseaseOssifying fibromaMeningiomaFibrous dysplasiaOssifying fibromaMenigioma

IdiopathicSpontaneous

drainage ofmucocele

(Continued) 171

SKULL BASE SURGERYNOLUME 4, NUMBER 3 JULY 1994

Authors Year

Meyers et al1980

Morrison et al1976

Noyek et al1974

Prott 1977

Reicher et al1986

Schayk et al1992

Seur et al1976

Seutin et al1979

Smith et al1987

Som et al1983

Spoor et al1981

Steinberg1969

Stretch 1992

Strottman etal 1992

Sugita et al1977

Tovi et al1991

Urken et al1987

Vines et al1976

Wiggli et al

Table 1. (Continued)Bony Defect

Type Sex Age Location (Yes/No) Symptoms Origin

Pneumocele M 25 Maxillar R Y Swelling Valve

Pneumocele M 45 Maxillar L

Pneumocele M 35 Maxillar R

PSDPSDPSD

PSDPneumocele*Pneumocele*

PSDPSDPSD

M 24 FrontalM 28 FrontalM 14 Sphenoid

M 45 SphenoidM 26 SphenoidF 31 Sphenoid L

M 17 SphenoidM 16 Fron, eth, sphM 15 Sphenoid R

(other case no true PSD)PSDPSDPSDPSDPSD

M

FM

M

M

33 Sphenoid60 Sphenoid33 Sphenoid33 Sphenoid21 Frontal L+R

Pneumocele M 48 Sphenoid

PSD F 18 Frontal +sphenoid

PSD

PSD

PSD

PSD

PSD

PSDPSDPSDPSD

PneumocelePneumocelePneumocele

PSD

PSD

PSDPSD

PSD

Williams et al PSD1975

Wolfensberger Pneumoceleet al 1987

Zismor et al Pneumocele1975

M 26 Frontal R

M 17 Pansinus

F 58 Ethmoid

M 26 Sphenoid

M 20 Maxillar L

FM

M

FM

M

F

80 Frontal L45 Frontal L+R37 Frontal L56 Frontal33 Frontal R36 Frontal62 Maxillar R

M 47 Sphenoid

M 56 Dorsal ethmoidSphenoid

M 67 SphenoidF 49 Dorsal ethmoid

SphenoidM 56 Sphenoid

M 73 Sphenoid

M 15 Maxillar R

F 13 Maxillar R

Y Pain, fullness

Y Pain, fullness

Not knownNot known

N

Nyy

NN

Not knownNot knownNot knownNot known

N

PainSwellingProptosis, loss of

visionSinusitis, headachesSinus headachesHeadaches,

glactorrheaAsymptomaticAsymptomaticFrontal headaches

Eye painUnspecificPsychiatric disorderAnosmiaSwelling

Y Temporary loss ofvision

N Loss of vision

Not known Swelling

N Loss of vision

N Vertigo

Not known Temp. bilat. toss ofvision

N Swelling

NNNNyyy

AsymptomaticAsymptomaticSwellingSwellingPain, swellingPain, swellingProptosis

N Loss of vision,hyposmie

N Loss of vision,hyposmie

N Loss of visionN Loss of vision

N Loss of vision,anosmie

N Loss of vision

Y Pain, exophthalmus

Y Nasal obstructionExopthalmus

Valve

Valve

IdiopathicIdiopathicIdiopathic

IdiopathicIdiopathicIdiopathic

HydrocephalusHydrocephalusArachnoid cyst

MeningiomaMeningiomaMeningiomaMeningiomaIdiopathic

Valve

Klippel-Trenaunaysyndrome,meningioma

Idiopathic

Melnick-Needlessyndrome,osteodysplasia

Arachnoid cyst

Idiopathic

Idiopathic

IdiopathicIdiopathicIdiopathicIdiopathicIdiopathicIdiopathicValve

Meningioma

Meningioma

MeningiomaMeningioma

Meningioma

Idiopathic

Valve

Valve

172 *Defined as a PSD with a bony defect by author, reclassified as pneumocele.

PNEUMOSIN US Dl LATANS-BACHOR ET AL

Table 2. Patients with Idiopathic Pneumosinus Dilatansfrom the Literature 1969 to 1992 Inclusive Case Report

Average AverageAge Age

Location Male (Years) Female (Years) TotalFrontal 10 28.5 3 68.7 1 3PSD

Maxillar 2 16.5 1 36 3PSD

Ethmoid 1 76 1PSD

Sphenoid 6 35.5 1 76 7PSD

Total 18 29.5 6 65.7 24Range= 13-73 Range = 36-80Median = 25.0 Median = 73.0

(54.2%), then the sphenoid sinus (29.2%). The ratio offemales to males was 1:3 (Table 2).

Pneumoceles were most common in the maxillary

sinus in males (35.3%). The ratio of females to males was

1:3.3 (Table 3).

DISCUSSION

Since the initial description of PSD there has beensome controversy about defining this entity. Benjamins2first reviewed 5 cases of PSD (initially reported by Meyesin 18981) in the literature and added 1 case of his own, inwhich he differentiated PSD from pneumocele. Pneumo-sinus dilatans was defined as a large, air-containing sinuscavity that enlarges slowly. The bony walls are intact andthere is no air outside the bony cavity or in soft tissue.There is no change in pressure. A sinus pneumocele orpneumatocele was described as an enlarged sinus with airin soft tissues communicating through a hole in the bonywall of the sinus. There is air present in soft tissue onforced expiration. The symptoms have a sudden onset.2,20In a recent publication Urken et al investigated 100 normal

Table 3. Patients with a Pneumocelefrom the Literature 1969 to 1992

Average AverageAge Age

Location Male (Years) Female (Years) TotalFrontal 3 29 1 44 4pneumocele

Maxillar 6 34 2 37.5 8pneumocele

Ethmoid 1 47 1pneumocele

Sphenoid 3 30.7 1 31 4pneumocele

Total 13 33.1 4 37.5 17Range = 15-51 Range = 13-62Median = 33.0 Median = 37.5

frontal sinus films and calculated a 99th percentile for the"normal" expansion of a frontal sinus.37 They suggested anew definition of "hyperpneumatisation" or "hypersinus"for frontal sinuses which have developed beyond the upperlimits of normal. These sinuses were aerated and theirwalls were normal. If the sinus walls were outwardlydisplaced, Urken et al defined it as PSD. If a bone defectwas present it was described as a pneumocele. The authorspostulated that the three forms of abnormally enlargedsinuses may be the same entity with different degrees ofmanifestation.21 Tovi et a138 proposed the label "air cyst"to avoid confusion between different etiologies of abnor-mally large paranasal sinuses. Because PSD or pneumo-cele is a radiological diagnosis, Reicher et al19 and Drosset a18 favor the term PSD to describe a dilated sinusregardless of etiology or association. In 1968 Lombardiet al reported on 51 patients with pneumosinus dilatans.Thirty-nine of the cases involved the frontal sinus, 5involved the anterior ethmoid sinus, 5 the posterior eth-moid and the sphenoid sinus, and 2 the maxillary sinus.They postulated that certain areas of the paranasal sinuseshave a predilection for developing pneumosinus dilatans,such as the lateral recess of the frontal sinus, the superiorrecess of the maxillary sinus, the region of the sella turcicaat the ethmoid-sphenoid junction, and the anterior eth-moids. In their series of PSD there were more males thanfemales and patients ranged in age from 20 to 40 years. Inour literature review of PSD a similar age and sex distribu-tion was found. Males with PSD ranged in age from 13 to73, with an average age of 29.5 years (Table 2). Pneumo-sinus dilatans was even more rare in females. The averageage of the 6 female patients is 65.6 years. Because of thesmall sample size it is not clear if this represents a truedifference in age distribution between males and females.The apparent rarity of documented ethmoid PSD (onlyone case reported39) may be because of the difficulty ofdefining a PSD in the highly variable ethmoid sinus.Pneumoceles seems to occur slightly more in males, al-though the average ages between the sexes are very similar.

The first case of a patient with unilateral temporaryamaurosis in a sphenoid sinus pneumocele was describedby Som et al.32 The patient reported blurred vision in hisleft eye during flying. Our patient reported no complaintswhen flying, probably due to adequate maintenance ofcabin pressure. In a report by Som et a132 the computerizedtomography revealed that the bone forming the sphenoidsinus wall was replaced by a thin soft-tissue membranousstructure. In our case we were unable to demonstrate a lossof bone of the sphenoid sinus wall, except for the area wefound along the optic nerve. However, Renn et a140 re-ported in an anatomical study of 50 adult sellae that 4% ofoptic canals had bone defects exposing the optic nerve inthe sphenoid sinus.

In our patient with PSD, ventilation of the sinusseemed to be disturbed. Two explanations are possible:

1. Air is temporarily trapped within the sphenoidsinus due to a valvelike mechanism at the os- 173

SKULL BASE SURGERYNOLUME 4, NUMBER 3 JULY 1994

tium. A subsequent decrease in ambient pres-sure (as with high altitude) results in a relativeincrease in intrasinus pressure that compressesthe optic nerve and its blood supply.

2. There is a decrease in pressure in all of theparansal sinuses resulting in a suction effect onthe optic nerve and its blood vessels. It appearsthat temporary blindness occurs only when theoptic canal is dehiscent. This would also explainthe extremely rare occurrence of such an event.

The first theory is favored by Sugita et al,41 whodescribed a similar patient with bilateral transient amau-rosis. They proved the postulated mechanism by placingthe patient in a hyperbaric chamber and lowering theatmospheric pressure. We did not test our patient in ahyperbaric chamber because we saw the exposed opticnerve on the computed tomogram. Sugita et al did not statewhether they believed that the symptoms resulted fromexcess or low pressure in the sphenoid sinus. As with ourpatient, Som et a132 used a transnasal approach to removethe anterior wall of the sphenoid sinus, and the patientremained free of symptoms. This procedure seems toestablish a pressure equilibrium in our and other patients,but which mechanism was the cause of the optic nervedysfunction is still speculative. In future patients with thisrare entity, testing in a hyperbaric chamber while opticfunction is monitored may be helpful in clarifying theprecise mechanism that causes the change in function ofthe optic nerve.

Pneumosinus dilatans can be classified as primary(idiopathic)19,21 22,39,42-49 or secondary4-18 SecondaryPSD can occur in fibrous-osseous disease4,5 and in con-genital syndromes like Melnick-Needles'1 or Klippel-Trenaunay-Weber.10 Pneumosinus dilatans is frequentlyseen in patients with brain anomalies and long-term shunt-ing, according to van Schayck and Niedeggen.6 Theypostulate that decreased intracranial pressure results inless compression of the surrounding skull bone and allowsfor more expansion of the sinuses.

Optic nerve meningioma with associated PSD mustbe considered in the differential diagnosis, especiallywhen vision decreases slowly. 12-18 This could be excludedin our patient by high resolution computed tomography.Meyer-Breiting reported a patient with transient decreasein vision, double vision, and proptosis with chronic-polypoid maxillary and ethmoid sinusitis and PSD. Henoted a spontaneous drainage of a mucocele as the etiol-ogy of the PSD.27 Benedikt et a150 also discussed sponta-neous drainage of ethmoid sinus mucocede as a possiblecause of PSD. In contrast, our patient had no signs ofinflammation.

Creation of a wide communication between the sinusand the nasal cavity was curative in all patients with PSDand pneumocele.32,41 In our patient a microendoscopicresection of the anterior wall allowed proper pressureequilibrium in the sphenoid sinus and prevented perma-

174 nent optic nerve damage. In patients with disturbing cos-

metic deformity due to bulging in the frontal and maxil-lary sinuses, resection of part of the enlarged sinus hasbeen shown to improve cosmetic appearance.39,4244-48

CONCLUSION

Temporary blindness associated with dilatation of thesphenoid sinus is extremely rare. According to the litera-ture available to us, our case is only the third one. Thepatient is a 37-year-old male with PSD of unknown etiol-ogy; however, a valvelike mechanism was postulated. Inaddition, the optic nerve was not covered by bone withinthe sphenoid sinus. A similar case described by Sugita eta141 presented with bilateral amaurosis. In patients withunclear recurrent loss of vision, dilatation of the sinuses,pneumosinus dilatans, or pneumocele should be consid-ered in the differential diagnosis. Intracranial masses suchas arachnoidal cysts or a meningioma should be ruled outby appropriate imaging studies.

In patients with a PSD of the sphenoid sinus andtransient amaurosis, endonasal microendoscopic resec-tion of the anterior wall of the sphenoid sinus establishespermanent pressure equilibrium and prevents permanentdamage of the optic nerve.

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The authors thank Gregory Grillone, M.D., for reviewing thearticle.

REVIEWER'S COMMENTS

The authors report a relatively unique case of apparent pneumosinus dilatans affecting thesphenoid sinus such that there was lack of bone along the medial wall of the left optic canal. Thepatient experienced two episodes of transient loss of vision in the left eye during mountainclimbing. Following endoscopic surgery to remove the anterior wall of the sphenoid sinus, thepatient had no further episodes of visual loss. The authors postulate a ball valve effect of trappedair at normal atmospheric pressure maintaining pressure against the intracanalicular portion of theoptic nerve as transferred through the area of absent bone while the rest of the nerve is underreduced atmospheric pressure. Although it is unclear to me whether or not this is the explanation, itwould seem clear from this case as well as several others reviewed by the authors that pneumosinusdilatans may produce both permanent and transient visual loss when the process affects thesphenoid region and that such visual loss can occur in the absence of any other associated lesion(eg, a meningioma). Furthermore, decompression of the sphenoid sinus seems to be effective ineliminating the episodes of transient visual loss and should be considered in all such cases. Finally,the authors have done an excellent job in reviewing cases of PSD in the literature and of describingtheir location, associated lesions, clinical manifestations, and treatment. This article is a welcomeaddition to the literature on this most interesting syndrome.

Neal Miller, M.D. 175