Blow-in fracture of both orbital roofs caused by shear strain to the skull. Department of Neurosurgery, Kanto Teishin Hospital, Tokyo, Japan

Transcription

1 J Neurosurg 49: , 1978 Blow-in fracture of both orbital roofs caused by shear strain to the skull Case report OSAMU SATO, M.D., HIROSHI KAMITANI, M.D., AND TAKASHI KOKUNAI, M.D. Department of Neurosurgery, Kanto Teishin Hospital, Tokyo, Japan v' The authors report a case with blow-in fractures of both orbital roofs caused by horizontal shear strain to the skull. The mechanism of the injury is discussed. Ophthalmic symptoms were improved by removal of intraorbital bone fragments and by repair of the orbital roof defects with methyl methacrylate. KEY WORDS 9 orbital fracture 9 orbital roof 9 blow-in fracture O F all fractures of the orbital wall, orbital floor "blow-out" fracture is the most common. Orbital roof fracture, on the other hand, is rare and is usually combined with more extensive craniofacial injuries. We encountered an unusual case of bilateral depressed fractures of the orbital roof caused by a horizontal shear strain injury to both temporal bones. There were no facial injuries. Case Report On September 20, 1976, this 29-year-old woman slipped off a railway platform and was struck on both temples between the platform and a train that was pulling in. She lost consciousness soon after the accident and was admitted to a local hospital. There were scalp lacerations on both temporal regions. Copious bleeding from the torn right superficial temporal artery was stopped by ligation of the artery. The day after the accident she regained consciousness, and was transferred to our hospital for appropriate treatment. Examination. On admission, she was drowsy and suffering from nausea and vomiting. Bilateral periorbital ecchymosis and swelling were noted. Pupils were myotic and sluggish to light on both sides. There was no restriction of eyeball movements, and fundoscopic examination revealed no choked discs or retinal bleeding. Otherwise, no abnormal neurological findings were elicited. Plain x-ray films revealed a large depressed skull fracture (12 X 4.5 cm wide and 1 cm deep) in the right frontotemporal region (Fig. 1). Water's projection showed a fracture of the right pterion and some abnormal shadows near the left orbital roof. The anteroposterior view of the right carotid angiograms revealed moderate shift of the anterior cerebral artery; the deep cerebral veins were also displaced by 8 mm, but there was no avascular area. First Operation. On September 27, a right frontotemporal craniotomy was performed for repair of the depressed fracture. The compound bone fragments were rongeured away, and the depressed bone fragment was elevated. There was no accumulation of ex- 734 J. Neurosurg. / Volume 49 / November, 1978

2 Blow-in fracture of orbit FIG. 1. Skull films, lateral (left) and anteroposterior (right) views. A large depressed fracture is seen in the right frontotemporal region, 12 X 4.5 cm wide and 1 cm deep (arrows). tradural hematoma. On extradural inspection of the middle cranial fossa, the lateral part of the sphenoid ridge was seen to be broken and multiple fracture lines were observed on the base of the middle fossa. On opening the dura mater, slight cerebral contusion was noted along the Sylvian fissure, but there was no subdural accumulation of hematoma. The depressed bone fragment was raised and fixed in its normal position. The skull defect was repaired with methyl methacrylate. Postoperative Course. Although the bilateral periorbital ecchymosis and swelling improved after the cranioplasty, bilateral conjunctival chemosis and pulsating exophthalmos became apparent, especially on the left side. Eyeball movements were not restricted. Left carotid angiograms did not reveal a carotid-cavernous fistula, but the ophthalmic artery appeared abnormal (Fig. 2). On the lateral view, the distal branches of the ophthalmic artery were markedly stretched and displaced inferiorly, and the choroid crescent was flattened. Right carotid angiograms also revealed moderate stretch and inferiorly displaced distal branches of the ophthalmic artery. These findings suggested the presence of superior intraorbital mass effects, and detailed orbital radiological examinations were performed. Orbital tomograms revealed depressed fracture of the orbital roof on both sides (Fig. 3). There was no fracture of the rim. Computerized tomograms of coronal sections confirmed these fractures. Second Operation. A second operation was performed for repair of the depressed fractures of the orbits on October 26. With a coronal scalp incision, separate frontal bone flaps were reflected on both sides. On initial extradural approach to the left orbital roof, dura mater was found entrapped and torn by the edge of the depressed bone fragment. Herniated necrotic brain tissue extruding through the dural tear was sucked away, and the entrapped dura mater was released by removal of depressed bone fragments. There remained an oval bone defect of the orbital roof, cm wide, which was repaired with a methyl methacrylate plate. The dural defect was repaired with Lyodura. Extradural inspection of the right orbital roof revealed an oval depressed fracture of the roof into the orbit, 1.5 X 1.5 cm wide, but there was no dural tear or entrapment. The depressed bone fragment was removed and J. Neurosurg. / Volume 49 / November,

3 O. Sato, H. Kamitani and T. Kokunai FIG. 2. Left carotid angiogram revealing stretch and inferior displacement of the distal branches of the ophthalmic artery (single arrows) and a flattened choroid crescent (double arrows). the orbital roof defect repaired with a methyl methacrylate plate. Postoperative Course. The patient's postoperative condition was excellent. Conjunctival chemosis and pulsating exophthalmos disappeared. At follow-up examination 11/2 years after the operation, she was completely well without any ophthalmic symptom. Discussion Among orbital wall fractures, fracture of the orbital floor occurs most frequently? ~ After the classic reports by Lang a and Pfeiffer 6 describing this kind of fracture, Smith and Regan 7 gave it the name of "blowout fracture." They showed that this fracture was due to an explosive rise in the intraorbital pressure by a blunt impact to the orbit which caused the bone fragments to blow out into the maxillar or ethmoidal sinuses where the orbital wall was weak. There have been several reports of blow-out fractures since. "Blow-in fracture" of the orbit was described by Dingman and Natvig, 2 in It is the elevation of fractured fragments of the orbital floor into the orbit by a trauma to the anterior face of the maxilla with a sudden increase of intramaxillary antral pressure. Ziz- mor and Noyek 1~ reported that blow-in fracture of the medial orbital walls was caused by a direct force that shattered nasal bones and orbital walls. Linz 4 also described blow-in fracture of the lateral walls of the orbit. But this type of fracture is very rare. The mechanism in our case of blow-in fracture of the orbit was somewhat similar to those mentioned above. In our case, the horizontal shear strain to both temporal regions of the skull probably caused an explosive increase of intracranial pressure and the direction of the strain was converted to perpendicular components. The orbital roofs, which were the weakest structures within the cranium, were fractured and depressed down into the orbit. In this way, contrary to blowout fracture of the orbit, blow-in fracture of the orbit may be caused by an explosive rise of the periorbital pressure and thus the orbital wall was fractured and depressed into the orbit. We could not find a report of a blow-in fracture of the orbital roofs without direct facial injury, as in our case. Usually orbital wall fractures are comminuted and are caused by extensive craniofacial injuries?,8-1~ The presence of orbital roof fractures was difficult to diagnose early in our case, because of the lack of direct facial injuries. We would 736 J. Neurosurg. / Volume 49 / November, 1978

4 Blow-in fracture of orbit FIG. 3. Orbital tomograms revealing depressed fracture of the orbital roof on both sides (arrows). The depression was more prominent on the left side. Frontal projection (upper), right lateral projection (lower left), left lateral projection (lower right). like to stress that, if a patient shows ophthalmic symptoms and signs, even without facial injury, fracture of the orbital wall is possible. Treatment of orbital roof fractures, if necessary, is by reduction of the displaced fractures and release of entrapped structures? If fractured segments are difficult to retain in position, reconstruction of the orbital roof is mandatory. For reconstruction of the orbital roof, methyl methacrylate is recommended by Mayer, et al, 5 as in the reconstruction of the orbital floor. References 1. Bloem J J, Meulen JC, Ramselaar JM: Orbital roof fractures. Mod Probl Ophthalmol 14: , Dingman RO, Natvig P: Surgery of Facial Fractures. Philadelphia: WB Saunders, 1964, 380 pp J. Neurosurg. / Volume 49 / November,

5 O. Sato, H. Kamitani and T. Kokunai 3. Lang W: Traumatic enophthalmos with retention of perfect acuity of vision. Trans Ophthaimoi Soc UK 9:41-45, Linz AM: Blow-in fracture of the lateral wall of the orbit. Trans lnt Conf Oral Surg 4: , Mayer R, Brihaye J, Brihaye-van Geertruyden M, et al: Reconstruction of the orbital roof by acrylic prosthesis. Mod Probl Ophthalmol 14: , Pfeiffer RL: Traumatic enophthalmos. Arch Ophthalmol 30: , Smith B, Regan WF Jr: Blow-out fracture of the orbit. Mechanism and correction of internal orbital fracture. Am J Ophthalmol 44: , Stranc MF, Gustavson EH: Plastic surgery Primary treatment of fractures of the orbital roof. Proc R Soe Med 66: , Walsh FB, Hoyt WF: Clinical Neuroophthalmology, ed 3. Baltimore: Williams and Wilkins, 1969, pp Zizmor J, Noyek AM: Orbital trauma, in Newton TH, Potts DG (eds): Radiology of the Skull and Brain, Voi. 1, Book 2. St. Louis: CV Mosby, 1971, pp Address reprint requests to: Osamu Sato, M.D., Department of Neurosurgery, Kanto Teishin Hospital, 5-Chome, Higashi-Gotanda, Shinagawa-ku, Tokyo, Japan. 738 J. Neurosurg. / Volume 49 / November, 1978