| OCR Text |
Show J. Clin. Neuro-ophthalmol. 4: 9-13, 1984. Basal Encephalocele Presenting with Monocular Visual Loss MONICA L. MONICA, M.D., Ph.D. EDWARD S. CONNOLLY, M.D. RODNEY F. KALIL, M.D. Abstract A 23-year-old male was seen with acute onset of decreased vision in the right eye. There was no associated facial abnormality, optic disc abnormality, or previous history of head trauma. A computerized tomography scan of the head revealed a soft tissue density in the right ethmoidal sinus. Surgical decompression of the ethmoid sinus for a possible pyocele or mucocele revealed the mass to be cerebral cortex. Successful neurosurgical repair of the defect in the cribiform plate and amputation of the abnormal brain tissue was accomplished with restoration of vision. Encephaloceles are congenital malformations in which the brain, with or without meninges, herniates through a cranial defect. The majority occur in the occipital region with only 15% involving the anterior cranial fossa.! Anterior encephaloceles may be subdivided into sincipital types involving the nasofrontal area or the more rare basal group occurring along the cribiform plate or through the sphenoid bone. The incidence of basal encephaloceles is estimated to be one in 35,000 live births. 2 The following case is the first report of a basal encephalocele seen in an adult with acute onset of monocular visual loss and no associated midfacial or ocular abnormalities. Case Report A 23-year-old white male was seen in the ophthalmology department at Ochsner Clinic with a history of acute onset of decreased vision in the right eye over a period of 2 or 3 days (Fig. 1). The patient stated that he had a cold 1 week prior to the onset of decreased vision with associated general malaise and nasal congestion. He stated that his vision became more blurred, but From the Departments of Ophthalmology (MLM. RFK) and Neurosurgery (ESC), Ochsner Clinic and Alton Ochsner Medical Foundation. New Orleans. Louisiana. March 1984 denied pain or diplopia. He also denied any headache, head trauma, chills, fever, or neurological abnormalities. His ocular and medical histories were negative except for myopia. On examination, the patient was alert and oriented. His best-corrected visual acuity in the right eye was light perception and in the left eye was 20/20 with a -4.50 sphere. There was no facial abnormality or periorbital edema. There was 2 mm of ptosis of the right upper lid. The pupils were symmetrical and measured 3 mm. The right pupil was reactive 1-2+ on direct and consensual light testing with a 2+ Marcus Gunn sign. The left pupil was 3+ reactive on direct and consensuallight testing. Slit lamp examination was normal. Intraocular tensions by Goldmann tonometry were normal. Direct and indirect ophthalmoscopy revealed normal optic discs and no retinal abnormalities. A computerized tomography (CT) scan of the head with and without contrast medium was performed and revealed a soft tissue density filling the right posterior ethmoid air cells (Fig. 2). The lesion did not enhance with contrast. There was a questionable extension of the lesion posteriorly with bowing of the medial rectus muscle on the right side. The skull x-rays were normal, and sinus films revealed opacification of the right ethmoid air cells. Laboratory studies including serology were negative. The otolaryngology service recommended decompression of the ethmoid sinus for a possible pyocele or mucocele. The anterior wall of the sphenoid sinus was deficient, and there was a whitish membranous tissue filling the ethmoid and sphenoid sinuses. Biopsy of this mass revealed cerebral cortex. Immediately following surgery, a repeat CT scan showed essentially no change from the preoperative CT scan. Postoperatively, there was no evidence of cerebrospinal fluid (CSF) rhinorrhea. Polytomography of the anterior cranial fossa demonstrated a defect in the floor of the frontal fossa on the right, extending from the cribriform plate to the planum sphenoidale (Fig. 3). Bilateral carotid angiograms were performed which showed evidence of some of the anterior polar branches on 9 Basal Encephalocele-Monocular Visual Loss Figure 1. enotograpli ot" .lJ-year-ofa' wnlte maCe wno presented with acute visual loss in the right eye. There are no facial abnonnalities. the right descending into a sphenoethmoidal encephalocele. On December 11, 1981, the patient underwent a right frontal craniotomy with an intradural approach to the lesion. On elevating the right frontal lobe, a defect was seen in the cribriform plate measuring 8 mm in width and 3 cm in anteroposterior dimension. Abnormal brain tissue arising in the area of the olfactory nerve and bulb extended down into the defect. The dura actually appeared to extend down into the defect, and there was no evidence of trauma, hemorrhage, or infection in the area. This tissue mass was compressing the superior-medial aspect of the right optic nerve. The abnormal area of brain tissue was amputated. Microscopic evaluation showed gliotic brain tissue. The defect was filled with muscle and covered with a two-layer fascia lata graft tacked to the dura of the frontal fossa. The brain was then allowed to reexpand, and the wound was closed. Postoperatively, the patient had an uneventful course and was discharged on the eighth day with no evidence of CSF rhinorrhea and with the vision in the right eye improving from light perception to 20/70 with a constricted visual field. The patient was last examined on August 19, 1982, and his vision was 20/30 in the right eye with a full visual field. Figure 2. Computerized tomography scan of head demonstrating soft tissue density filling the right ethmoidal air cells. The lesion did not enhance with contrast. Journal of Clinical Neuro-ophthalmology Monica, Connolly, Kalil - ----- I I --- Figure 3. Tomography of anterior cranial fossa demonstrating clouding of the right ethmoid and maxillary sinus. The planum sphenoidale on the right side was absent. Discussion Encephaloceles are congenital malformations of the central nervous system in which cerebral tissue herniates through a bony defect in the skull. These malformations are classified according to anatomic location and whether or not they are externally visible. 3 - s The Hhidden" type or basal encephalocele is rare and occurs along the cribiform plate or through the sphenoid bone. Basal encephaloceles occur more commonly in Southeast Asian countries, such as Thailand, with a reported incidence of one in 5,000 live births. 6 Clues as to the diagnosis of a basal encephalocele may be detected by certain physical findings. The importance of midline facial abnormalities associated with this congenital malformation are well-documented.6 - 8 Anterior encephaloceles are associated with a broad nasal root, hypertelorism, increased bitemporal diameter, cleft lip, and cleft palate.7 - 9 Often what appears as a nasal polyp in a child is actually an intranasal enceph- March 1984 alocele. Early in childhood, the intranasal encephalocele may present with nasal discharge, respiratory obstruction, mouth breathing, or snoring. 7 . 8 A high index of suspicion for basal encephalocele must be maintained when a midline cystic nasopharyngeal mass with or without associated midfacial abnormalities is discovered in a child. 1O In the past, encephaloceles have been evaluated by routine x-rays, tomography, and pneumoencephalography, 10 but there are some pitfalls to linear tomography due to the thickness of the cuts produced. Prior to the advent of CT scans, some authors felt that pneumoencephalography was the most important way to diagnose frontoethmoidal encephaloceles, but they state that only a small proportion of the encerchaloceles are diagnosed solely by this procedure. 0.11 The study may also fail to demonstrate the herniated sac or the presence or absence of brain tissue within the sac. Pinto and co-workersl2 stated that basal encephaloceles are best evaluated by hypocloidal tomography and then magnification angiogra- 11 Basal Encephalocele-Monocular Visual Loss phy. In the three cases they presented, herniation of the anterior inferior frontal artery through an osseous defect of the cribiform plate occurred in the basal encephaloceles of the anterior fossa. The CT scan provides the single best test for diagnosing basal encephaloceles. Scans performed with settings for bone demonstrate the bony defect, and soft tissue settings will demonstrate the encephalocele. Density reading should help differentiate the soft tissue mass between brain, pyocele, cyst, or mucocele. Plain roentgenographs of the skull frequently fail to delineate any abnormality in basal encephaloceles. Various ocular signs and optic nerve anomalies have been reported with basal encephaloceles such as optic nerve head pits,I3 optic nerve coloboma/' 14. 15 optic disc drsplasia and megalopapilla, I6 optic disc pallor, I pulsatile exophthalmos and ocular palsies,18.19 microphthalmos,!? and peripapillary staphyloma.17 None of these associated ocular findings was evident in our case. Three cases have been reported of a meningo~ nceph.aloc~le causin~ nontraumatic cerebrospmal fluId rhmorrhea.2 -22 Another case of a 24year- old male with dysplastic optic discs and spontaneous cerebrospinal fluid rhinorrhea with recurrent bacterial meningitis due to a basal encephalocele was reported. 23 This young man demonstrated no midfacial abnormalities, but a large intranasal polyp was seen behind the left middle turbinate which produced a nasal discharge. Finally, a case of recurrent meningitis 20 years after head injury with absence of cerebrospinal fluid rhinorrhea was caused by an encephalocele. 24 It is important to avoid misdiagnosis of a small encephalocele as a nasal polyp since biopsy inadvertently may lead to postoperative CSF rhinorrhea and ensuing meningitis. Fortunately, there were no postoperative complications in our case. To our knowledge, this is the first reported case of a basal encephalocele presenting with an acute onset of monocular visual loss in a patient with no associated ocular or midfacial abnormalities. Streletz and Schatzl5 reported visual loss in a 34year- old male due to optic nerve and chiasmal compression by a transsphenoidal encephalocele, but the patient had associated findings of hypertelorism, short stature, hypopituitarism, and bilateral optic disc colobomas. In conclusion, our case could easily have been mistaken for acute visual loss in a young adult due to optic neuritis. It was fortuitous that a CT scan was obtained on this patient which led to further investigation and eventual diagnosis of the basal encephalocele. We should now include the possibility of a basal encephalocele in the list of disorders causing acute monocular visual loss which includes entities such as demyelinative disease, inflammation from contiguous structures (sinus, meninges or orbital tissues), fibrous dysplasia of bone,25 postviral infections, or granulomatous inflammations, aneurysms, and tumors (e.g., meningiomas). References 1. Ingraham, F.D., and Swan, H.: Spina bifida and cranium bifidum; a survey of 546 cases. N. Engl. J. Med. 228: 559-563, 1943. 2. Matson, D.D.: Neurosurgery in Infancy and Childhood (2nd ed.). Charles C Thomas, Springfield, Illinois, 1969, p. 68. 3. von Meyer, E.: Ueber einc BasaIe Hirahernie in der Gergend der Lamina Caroboda. Arch. Pathol. Amt. Physiol. Klin. Med. 120: 309-320, 1890. 4. Saframek, J.: Ueber die Nasalen Formen der Basalen Zephalozelen. Monatschr. Ohrenh. 60: 709-717, 1926. 5. Gisselson, L.: Intranasal forms of encephalomeningocele. Acta. Otolaryngol. 35: 519-531, 1947. 6. Suwanwela, c., and Hongsaprablas, c.: Frontoethmoidal encephalomeningocele. J. Neurosurg. 25: 172,1966. 7. Pollock, J.A., Newton, T.H., and Hoyt, W.F.: Transsphenoidal and transethmoidal encephaloceles. A review of clinical and roentgen features in 8 cases. Radiology 90: 442-453, 1968. 8. Modesti, L.M., Glasaner, F.E., and Terphan, K.L.: Sphenoethmoidal encephalocele. A case report with review of the literature. Child's Brain 3: 140153, 1977. 9. Dodge, H.W., Love, J.G., and Kennohan, J,W.: Intranasal encephalomeningoceles associated with cranium bifidum. Arch. Surg. 79: 75-84, 1959. 10. Suwanwela, c., and Suwanwela, N.: Air study in infants and children with fronto-ethmoidal encephalomeningocele. Neuroradiology 4: 190-194, 1972. 11. Tandon, P.N.: Meningoencephaloceles. Acta. Neurol. Scand. 46: 369-383, 1970. 12. Pinto, RS., George, A.E., Koslow, M., and Barasch, G.: Neuroradiology of basal anterior fossa (transethmoidal) encephaloceles. Neuroradiology 117: 79-85, 1975. 13. Van Nouhouys, J.M., and Bruyn, G.W.: Nasopharyngeal transsphenoidal encephalocele, crater-like hole in the optic disc and agenesis of the corpus callosium: Pneumoencephalographic visualization in a case. Psychiatr. Neural. Naurochir. 67: 243, 1964. 14. Lewin, M.C., and Shuster, M.M.: Transpalatal correction of basilar meningocele with cleft palate. Arch. Surg. 90: 687-693, 1965. 15. Streletz, L.J., and Schatz, N.J.: Transsphenoidal encephalocele associated with hypopituitary dwarfism. In Neuro-ophthalmology Symposium, J.L. Smith, and J. Glaser, Eds. C.V. Mosby Co., St. Louis, 1973, pp. 78-86. 16. Goldhammer, Y., and Smith, J.L.: Optic nerve Journal of Clinical Neuro-ophthalmology anomalies in basal encephalocele. Arch. Ophthalmol. 93: 115-118, 1975. 17. Walsh, F.B., and Hoyt, W.F.: Clinical Neuro-ophthalmology (3rd ed.). Williams & Wilkins Co., Baltimore, 1969. 18. Rovit, R.L., and Sosman, M.e.: Hemicranial aplasia with pulsating exophthalmos: An unusual manifestation of Von Recklinghansen's disease. J. Neurosurg. 17: 104-121, 1960. 19. Cullen, R.F., Jr., and O'Tuama, L.A: Hemicranial aphasia, proptosis, and neurofibromatosis. In Neuro-ophthalmology Symposium, J.L. Smith, Ed. C.V. Mosby Co., St. Louis, 1972, pp. 151-158. 20. Shugar, J.M., Som, P.M., Eisman, W., and Biller, H.F.: Non-traumatic cerebrospinal fluid rhinorrhea. Laryngoscope 91: 114-120, 1981. 21. Kane, AM., and Lore, J.: Meningoencephalocele of the paranasal sinuses. Laryngoscope 85: 20872091, 1971. 22. Drettner, B.: Encephalomeningocele in the frontal sinus. Acta. Otolaryngol. 57: 181-187, 1964. 23. Bullard, D.E., Crockard, A, and McDonald, W.F.: March 1984 Monica, Connolly, Kalil Spontaneous cerebrospinal fluid rhinorrhea associated with dysplastic optic discs and a basal encephalocele. Case Report. J. Neurosurg. 54: 807810,1981. 24. Sengupta, R.P., and Garvan, N.: Recurrent fulminating meningitis 20 years after head injury. J. Neurosurg. 41: 758-761, 1974. 25. Melen, 0., Weinberg, P.E., Kim, K.5., Hemmati, M., and Signicira, E.B.: Fibrous dysplasia of bone with acute visual loss. Ann. Ophthalmol. 12: 734739, 1980. Acknowledgment The authors thank Dr. Henry J.L. Van Dyke of the LSU Eye Center, Louisiana State University Medical Center in New Orleans, for reviewing this manuscript. Write for reprints to: Monica L. Monica, M.D., Ph.D., 1514 Jefferson Highway, New Orleans, Louisiana 70121. 13 |
