Pneumocephalus A
Sign of Intracranial Involvement in Orbital Fracture
George
O.
Waring III, MD, Joseph C. Flanagan,
Fractures of the orbit resulting from blunt or penetrating injury that involve the paranasal sinuses may tear the dura and allow air to enter the cranial cavity (pneumocephalus). Pneumocephalus is sometimes the only sign of intracranial involvement. It is characteristically delayed in onset and clinically unsuspected, so that routine follow-up roentgenograms of patients with orbitosinus fractures may be the only means ofassuring early detection. Roentgenographically, the airmaybe seen in epidural, subdural, subarachnoid, intracerebral, or intraventricular locations. Prophylactic parenterally administered antibiotics may prevent intracranial infection. However, since about 25% of patients still develop meningitis, surgical repair of the dural fistula is often necessary.
who examines with intracranial in¬ the volvement from an orbital fracture confronts a life-threatening situ¬ ation. A fracture or penetrating wound of the orbit that passes through a paranasal sinus and the base of the skull establishes a direct communication between the respira¬ tory passage and the brain—with the risk of meningitis and brain abscess. Cerebrospinal fluid (CSF) may flow out (CSF rhinorrhea) and air may flow in (pneumocephalus). The roent¬ genographic detection of intracranial
The ophthalmologist patient
Submitted for publication April 19, 1974. From the Oculoplastic Service, Wills Eye Hospital, Philadelphia. Dr. Waring is now at the University of California Medical College, Davis. Read before the Philadelphia College of Physicians, April 18, 1974. Reprint requests to Department of Ophthalmology, University of California Medical College, Davis, CA 95616 (Dr. Waring).
MD
air may be the only sign of a durai fistula. The ophthalmic literature contains three descriptions of pneumocepha¬ lus.1"3 It is omitted from recent text¬ books on orbital fracture.4 5 This pa¬ per reports a case of orbital fracture in which the onset of pneumocephalus two weeks after injury was the first sign of previously unsuspected intra¬ cranial involvement. REPORT OF A CASE On Dec 15, 1972, a 22-year-old man was operating a carbide grinding wheel when it shattered. He was seen at a community hospital with a deep, 12.7-cm (5-in) lacer¬ ation across the nasal bridge and left in¬ fraorbital area, severe left periorbital ec¬ chymoses, and chemosis. Visual acuity was 6/6 OD and no light perception OS. Roent¬ genograms showed multiple fractures of the floor and lateral wall of the left orbit. There was no loss of consciousness. Sys¬ temic penicillin G procaine and tetracycline were administered. At surgery, the findings included mul¬ tiple foreign bodies within the orbit, total hyphema and hypotony of the globe with¬ out an apparent rupture site, and avulsion of the inferior rectus and inferior oblique muscles. A comminuted compound fracture of the lateral orbital wall was wired, and a Teflon plate was inserted. Postoperatively, enophthalmos and severe chemosis pre¬ vented the visualization of the globe. Visual acuity test results showed that the patient had no light perception. The patient was transferred to Wills Eye Hospital. Orbital exploration on Dec 26, 1972, showed gross intraorbital hemor¬ rhage and a posteriorly ruptured globe that was enucleated. The postoperative course was satisfactory, and the patient was discharged on Dec 30. On Jan 1,1973, the patient blew his nose
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and noticed a gush of clear nasal fluid. The following day he returned to Wills Eye Hospital with a severe headache. He had marked lethargy, hyperacusis, meningism, and a positive Brudzinski sign. He was afebrile, and had a normal complete blood cell count. Skull x-ray Alms showed air fill¬ ing the cerebral ventricles, without dilata¬ tion or displacement. There was also an air-filled frontal intracerebral cyst con¬ necting the region of the right cribriform plate with the anterior horn of the right lateral ventricle (Fig 1). The patient was transferred to Lankenau Hospital where a spinal tap was per¬ formed that showed an opening pressure of 210 cm H20 and cloudy CSF, with 117 polymorphonuclear leukocytes, 444 lym¬ phocytes, and 123 red blood cells per cu¬ bic millimeter. The protein level was 83 mg/100 ml and glucose, 60 mg/100 ml. Cul¬ ture showed no growth in 48 hours. There was intermittent drainage of serosanguineous fluid from the nose from which hemolytic Staphylococcus aureus, a-hemolytic Streptococcus, and Neisseria catarrhalis grew on culture. The patient was treated intravenously with ampicillin so¬ dium. He remained afebrile and began to recover from his lethargy and meningism. After 24 hours, CSF rhinorrhea ceased, but air continued to fill the cerebral ventricles. On Jan 9, 1973, a bifrontal craniotomy was performed, disclosing a large defect in the dura on the right side, just above the cribriform plate. A portion of softened brain tissue extended downward, funnel¬ like, into the region of the cribriform plate. This portion of the brain was surgically re¬ tracted and the durai defect sutured. On the seventh postoperative day, a skull xray film showed complete clearing of the traumatic pneumocephalus. Four months after enucleation, an ocular prosthesis was fitted. The patient has remained free of neurological signs and symptoms for more than 18 months.
Fig 1.—Intracerebral and intraventricular pneumocephalus. Lateral (left) and frontal (right) skull roentgenograms taken two weeks following orbital fracture demonstrate air filling both lat¬ eral ventricles and third ventricle (t). Pear-shaped intracerebral pneumocephalus (black arrowheads) of right frontal lobe con¬ nects cribriform plate above nasal cavity (white arrowhead) to an¬ terior horn of lateral ventricle. Orbital fracture and ruptured globe occurred on left, while intracerebral pneumocephalus occurred on
right. COMMENT Previous Literature
There
many synonyms for pneumocephalus: cranial aerocele, pneumatocele, intracranial air pocket, are
pneumatocephalus, pneumocephalon,
cerebral
pneumocyst,
pneumoven-
the first
comprehensive report pneumocephalus. Markham44
viewed the literature up to 1967 and tabulated the findings of 295 cases. North,4- in 1971, added 41 cases of
posttraumatic pneumocephalus.
tricle, pneumocranium, pneumocele, and spontaneous ventriculogram.
Jelsma and Morre" credit Lecat7 for the first report of pneumocephalus. Chiari5 first demonstrated a mecha¬ nism of pneumocephalus formation when he found at autopsy an ethmoid sinus fracture associated with a durai tear that produced a pocket of air in the frontal lobe and air in the lateral ventricle. Luckett" published the first radio¬ logical description of pneumocephalus in a man who was struck by a trolley whose initial roentgenograms showed no intracranial air. After sneezing, he developed severe headaches and CSF rhinorrhea. Roentgenograms demon¬ strated a pneumocephalus that was confirmed at autopsy as coming from a fracture of the orbital roof, with a durai tear and a laceration of the frontal lobe that communicated with the lateral ventricle. Dandy1" made
on re¬
of
Pathogenesis Pneumocephalus
Fracture of the wall of a paranasal sinus allows the escape of air into ad¬ jacent tissue. Fractures of the medial orbital wall, involving the ethmoid si¬ nuses, are often associated with orbi¬ tal emphysema.4 Fracture of the an¬ terior wall of the frontal sinus may result in subperiosteal emphysema (extracranial pneumatocele)." Frac¬ tures of the inner wall of the frontal ethmoid, sphenoid, or mastoid sinus may allow air to pass intracranially, '"
forming
a
pneumocephalus.
Orbital roof fractures from blunt or
trauma are likely to be associated with pneumocephalus for three reasons4446: 1. The orbital plate of the frontal bone is thin and easily fractured. In blunt injury, orbital roof fracture may be associated with nasal trauma
penetrating
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in which the perpendicular plate of the ethmoid is forced upward, frac¬ turing the cribriform plate with re¬ sultant continuity between the nasal and intracranial cavity.5 2. The orbital roof may contain an extension of the frontal or ethmoid sinuses, so that a fracture can estab¬ lish continuity between the sinus and intracranial cavity (Fig 2). 3. The dura over the orbital roof is thin and firmly anchored by its exten¬ sions through the bone along the ol¬ factory nerves, so that roof fractures are usually associated with a durai tear. A durai tear tends to remain patent because the dura is a poorly healing tissue. In addition, brain, arachnoid, bone, or sinus mucosa may be incarcerated in the defect.47 Air passes through the durai tear by one of two mechanisms:17 (1) Ball Value—air may be forced through the durai tear during coughing, sneezing, or straining. After this pressure wave, the tear is sealed by brain or meningeal tissue, trapping the air in¬ side. Repeated instances of this could raise intracranial pressure. (2) Nega¬ tive Pressure—If a CSF leak is excès-
sive, a negative pressure may be created, sucking air in through the durai defect.
Roentgenographic Appearance of Pneumocephalus The air distributes itself intracranially along anatomic spaces, each of which has a characteristic roentgeno¬ graphic appearance (Fig 3) and pathogenic mechanism.6111218 Epidural pneumocephalus results if no durai tear is present. It is rare (7.1% of cases),41 and usually results from processes that erode the bone but not the dura. Roentgenograms demonstrate a small loculated collec¬ tion of air that does not move on change of position. Subdural pneumocephalus is more common (28.1% of cases),11 and usu¬ ally accompanies fractures or tumors of the frontobasal region that pro¬ duce a durai defect. The air moves freely, distributes itself over the hem¬ isphere, may outline the falx cerebri or tentorium, and may form an airfluid level. Subarachnoid pneumocephalus re¬ quires a tear in the arachnoid. The air often spreads through the foramina of Luschka and Magendie to the cere-
Fig 2.—Pathogenesis of pneumo¬ cephalus. Skull and black pencil dem¬ onstrate one pathway that a penetrating orbital missile could take to produce a pneumocephalus. It enters orbit in a su¬ peromedial direction, penetrates thin orbi¬ tal roof, passes through extension of fron¬ tal sinus, and enters anterior cranial fossa. bral ventricles, as is seen in a diag¬ nostic pneumoencephalogram. Subarachnoid and intraventricular air are present alone or in combination in about 20% of cases of pneu¬
mocephalus.44 Roentgenographically,
the air outlines the cortical spaces
Fig 3.—Possible locations of intracranial air: E, epidural; D, subdural; C, intracerebral; V, intraventricular; A, subarachnoid. Air may enter cranium from nasal cavity (n), frontal sinus (f), ethmoid sinuses (e), or sphenoid sinus (s).
and basal cisterns and shifts on change of position. Subarachnoid air most commonly results from commu¬ nication between the posterior eth¬ moid or sphenoid sinuses and the ba¬ sal cisterns. Intracerebral pneumocephalus oc¬ curs when the brain and dura adhere to the fracture, so that air does not spread beneath the meninges, but penetrates the brain substance directly. The air remains intracere¬ bral in about 25% of cases.14 In an ad¬ ditional 10%, a cerebral necrosis is present that allows the air to enter the ventricles, as in our patient (Fig 1). The intracerebral air pattern ex¬ tends upward from the floor of the anterior fossa or backward from the region of the frontal sinus. It has a pear or funnel shape, the narrow neck of which leads to its source. Combina¬ tions of the various locations occur in about 20% of cases.41 In our patient, the durai tear and intracerebral pneumocephalus were on the right, while the orbital frac¬ ture and ruptured globe were on the left. The probable mechanism is that a fragment of the shattered grinding wheel struck the left orbit with a force directed superomedially that drove the nasal bones up to the right, fracturing the right side of the cribri¬ form plate and lacerating the over¬ lying meninges and frontal lobe. Al¬ ternatively, a piece of the grinding wheel may have penetrated the roof of the left orbit in a superonasal di¬ rection, passing through the ethmoid or frontal sinus into the right ante¬ rior cranial fossa. The absence of an intracranial foreign body and the connection of the frontal lobe pneu¬ mocephalus to the right cribriform plate area make this mechanism un¬
likely.
Clinical Characteristics and of Pneumocephalus
Diagnosis
Pneumocephalus occurs in less than
1% of
cases
of head trauma, but is
present in about 8% of fractures in¬
the nasal sinuses.11'47 The cause of pneumo¬ cephalus is frontocranial trauma from traffic accidents or missile injuries, accounting for about 75% of cases. Other causes include osteomas of the
volving most
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common
paranasal sinuses (13%), sinusitis (9%), and surgical fistulas (4%).41
Intracranial involvement in pene¬ trating orbital injuries commonly es¬ capes early detection, as Bard and Jarrett noted in their analysis of 53 cases.14 The wound is often small and of uncertain direction. The severe ocular damage detracts attention from the intracranial injury. Roent¬ genographic studies are unreliable in detecting small associated fractures. When symptoms and signs do occur, they are often nonspecific. Headache,
meningism, stupor, or papilledema findings compatible with subdural hematoma, brain abscess, meningitis, and pneumocephalus.10 Pneumocephalus usually has a de¬ layed onset and is clinically silent. It are
is seldom
seen on
initial skull x-ray
films, and remains unsuspected until it appears
as a startling discovery subsequent roentgenograms. Pre¬ sumably, the durai defect is initially sealed by edema or a hematoma. As these resolve or as they are dislodged by sneezing or straining, air is forced
on
into the cranium. About one fourth of develop in the first week, half within the first month, and three fourths by three months after injury. Only 5% develop after one year.11 Thus, in order to detect the asympto¬ matic and delayed onset of pneu¬ mocephalus, skull roentgenograms must be repeated periodically on pa¬ tients with fractures of the paranasal sinuses. The brow-up position with a hori¬ zontal beam is most helpful, since it allows the air to collect superiorly, creating an air-fluid level.12·18 Detec¬ tion of a small pneumocephalus may require multiple head positions to demonstrate shifts of the air pattern, stereoscopic roentgenograms, and tomograms. Even in the presence of pneumocephalus and orbital injury, the most rigorous roentgenographic examination will often fail to disclose the small fracture in the frail orbital roof. Rarely, the patient will report hearing a splashing sound when he moves his head. This succussion splash can be verified by cerebral ascultation, and probably represents the movement of fluid within the air cases
cavity.11 Cerebrospinal fluid rhinorrhea and pneumocephalus have the same clini¬ cal significance: a break in the dura
with risk of intracranial infection. Observable CSF rhinorrhea accom¬ panies pneumocephalus in about 25% of cases.111217 Pneumocephalus is often a better clue in the detection of intracranial involvement, since it is present consistently, while a CSF leak is usually intermittent. A frac¬ ture or penetrating injury of the orbit that does not connect to a nasal sinus may allow CSF to leak directly into the orbit, producing lid swelling and proptosis.1719 In some of these in¬ stances, the CSF flows out of the orbi¬ tal wound (CSF orbitorrhea).'4'20-21 Treatment of Durai Fistula.—The chief aim in the treatment of orbital fractures with intracranial involve¬ ment is the prevention of meningitis and brain abscess. Pneumocephalus is merely a sign of the durai tear, and the air will be absorbed when the tear is sealed. Prompt parenteral adminis¬ tration of broad-spectrum antibiotics may prevent CNS infection. If the durai tear heals spontaneously, surgi¬ cal intervention may be avoided.1114 However, about 25% of patients with durai lacerations develop meningitis, and some surgeons advocate prompt operative repair.12·17-22 Markham11 has listed the following indications for the surgical treatment of pneumo¬ cephalus: (1) delayed healing of the durai defect, allowing persistent pneumocephalus or CSF rhinorrhea, (2) recurrence of pneumocephalus or CSF rhinorrhea, (3) neoplasm or si¬ nusitis that creates a persistent path¬ way for ingress of air, and (4) the presence of an intracerebral pneu¬ mocephalus, which implies adherence of the brain to a fistulous tract. In all cases, individual considerations and neurosurgical consultation will vary the final decision. In the presence of a known orbitosinus-cranial fistula, foreign material, such as wires and alloplastic plates, should not be used in repair of orbital fractures, because they may increase the chance of infection. Repair of the orbital damage may have to be de¬ layed until the durai fistula can be sealed.
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This investigation was supported in part by the Heed Ophthalmic Foundation (Dr. Waring). Paul L. Carmichael, MD, referred the patient. Randall W. Bell, MD, reviewed the manu¬
script.
Key Words.—Pneumocephalus; orbital fracture; meningitis; cerebrospinal fluid (CSF) rhinorrhea; aerocele; paranasal
sinus fracture.
References 1. Slaughter H, Alvis BY: Pneumo-encephalocele secondary to a puncture wound to the lid. Am J Ophthalmol 27:617-620, 1944. 2. Unger HH, Umbach W: Transorbitale Schadelhirntraumen durch Fremdkorper. Klin Monatsbl Augenheilkd 140:269-281, 1962. 3. Bard LA: Pneumocephalus secondary to a penetrating orbital wound. Arch Ophthalmol 70:232-235, 1963. 4. Milauskas AT: Diagnosis and Management of Blowout Fractures of the Orbit with Clinical, Radiological, and Surgical Aspects. Springfield, Ill, Charles C Thomas Publisher, 1969. 5. Hotte HA: Orbital Fractures. Assen, Holland, Van Gorcum, 1970. 6. Jelsma F, Moore DF: Cranial aerocele. Am J Surg 87:437-451, 1954. 7. Lecat J: Arch Gen Med (Paris) 1:34-55,1866. 8. Chiari H: Uber einen Fall von Luftensammlung in der ventrickein der menschlichen gehirns. Z Heilk 5:383-390, 1884. 9. Luckett WH: Air in the ventricles of the brain following a fracture of the skull. Surg Gynecol Obstet 17:237-240, 1913. 10. Dandy WE: Pneumocephalus (intracranial pneumatocele or aerocele). Arch Surg 12:949-982, 1926. 11. Markham JW: The clinical features of pneumocephalus based upon a survey of 284 cases with report of 11 additional cases. Acta Neurochir 16:1-78, 1967. 12. North JB: On the importance of intracranial air. Br J Surg 58:826-829, 1971. 13. Bard LA, Jarrett WH: Intracranial complications of penetrating orbital injuries. Arch Ophthalmol 71:332-343, 1964. 14. Duffy GP, Bhandari YS: Intracranial complications following transorbital penetrating injuries. Br J Surg 56:685-688, 1969. 15. Guthkelch AN: Apparently trivial wounds of the eyelids with intracranial damage. Br Med J 2:842-844, 1960. 16. Grote W: Traumatic fronto-basal liquorrhea-fistulae: Experiences with 112 operation cases, in DeVet AC (ed): Proceedings of the Third International Congress of Neurological Surgery. New York, Excerpta Medica, 1966. 17. Lewin W: Cerebrospinal fluid rhinorrhea in nonmissile head injuries. Clin Neurosurg 12:237-252, 1964. 18. Eaglesham DC: Radiological aspects of intracranial pneumocephalus. Br J Radiol 18:335\x=req-\ 343, 1945. 19. Bagolini B: Leakage of spinal fluid into upper lid following trauma. Arch Ophthalmol 57:454-456, 1957. 20. Ide CH, Webb RW: Penetrating transorbital injury with cerebrospinal orbitorrhea. Am J Ophthalmol 71:1037-1039, 1971. 21. McClure CC Jr, Gardner WJ: Transorbital intracranial stab wounds. Cleve Clin Q 16:118\x=req-\ 125, 1949. 22. Looking for the leak, editorial. Lancet 1:134-135, 1972.
Sign of Intracranial Involvement in Orbital Fracture
George
O.
Waring III, MD, Joseph C. Flanagan,
Fractures of the orbit resulting from blunt or penetrating injury that involve the paranasal sinuses may tear the dura and allow air to enter the cranial cavity (pneumocephalus). Pneumocephalus is sometimes the only sign of intracranial involvement. It is characteristically delayed in onset and clinically unsuspected, so that routine follow-up roentgenograms of patients with orbitosinus fractures may be the only means ofassuring early detection. Roentgenographically, the airmaybe seen in epidural, subdural, subarachnoid, intracerebral, or intraventricular locations. Prophylactic parenterally administered antibiotics may prevent intracranial infection. However, since about 25% of patients still develop meningitis, surgical repair of the dural fistula is often necessary.
who examines with intracranial in¬ the volvement from an orbital fracture confronts a life-threatening situ¬ ation. A fracture or penetrating wound of the orbit that passes through a paranasal sinus and the base of the skull establishes a direct communication between the respira¬ tory passage and the brain—with the risk of meningitis and brain abscess. Cerebrospinal fluid (CSF) may flow out (CSF rhinorrhea) and air may flow in (pneumocephalus). The roent¬ genographic detection of intracranial
The ophthalmologist patient
Submitted for publication April 19, 1974. From the Oculoplastic Service, Wills Eye Hospital, Philadelphia. Dr. Waring is now at the University of California Medical College, Davis. Read before the Philadelphia College of Physicians, April 18, 1974. Reprint requests to Department of Ophthalmology, University of California Medical College, Davis, CA 95616 (Dr. Waring).
MD
air may be the only sign of a durai fistula. The ophthalmic literature contains three descriptions of pneumocepha¬ lus.1"3 It is omitted from recent text¬ books on orbital fracture.4 5 This pa¬ per reports a case of orbital fracture in which the onset of pneumocephalus two weeks after injury was the first sign of previously unsuspected intra¬ cranial involvement. REPORT OF A CASE On Dec 15, 1972, a 22-year-old man was operating a carbide grinding wheel when it shattered. He was seen at a community hospital with a deep, 12.7-cm (5-in) lacer¬ ation across the nasal bridge and left in¬ fraorbital area, severe left periorbital ec¬ chymoses, and chemosis. Visual acuity was 6/6 OD and no light perception OS. Roent¬ genograms showed multiple fractures of the floor and lateral wall of the left orbit. There was no loss of consciousness. Sys¬ temic penicillin G procaine and tetracycline were administered. At surgery, the findings included mul¬ tiple foreign bodies within the orbit, total hyphema and hypotony of the globe with¬ out an apparent rupture site, and avulsion of the inferior rectus and inferior oblique muscles. A comminuted compound fracture of the lateral orbital wall was wired, and a Teflon plate was inserted. Postoperatively, enophthalmos and severe chemosis pre¬ vented the visualization of the globe. Visual acuity test results showed that the patient had no light perception. The patient was transferred to Wills Eye Hospital. Orbital exploration on Dec 26, 1972, showed gross intraorbital hemor¬ rhage and a posteriorly ruptured globe that was enucleated. The postoperative course was satisfactory, and the patient was discharged on Dec 30. On Jan 1,1973, the patient blew his nose
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and noticed a gush of clear nasal fluid. The following day he returned to Wills Eye Hospital with a severe headache. He had marked lethargy, hyperacusis, meningism, and a positive Brudzinski sign. He was afebrile, and had a normal complete blood cell count. Skull x-ray Alms showed air fill¬ ing the cerebral ventricles, without dilata¬ tion or displacement. There was also an air-filled frontal intracerebral cyst con¬ necting the region of the right cribriform plate with the anterior horn of the right lateral ventricle (Fig 1). The patient was transferred to Lankenau Hospital where a spinal tap was per¬ formed that showed an opening pressure of 210 cm H20 and cloudy CSF, with 117 polymorphonuclear leukocytes, 444 lym¬ phocytes, and 123 red blood cells per cu¬ bic millimeter. The protein level was 83 mg/100 ml and glucose, 60 mg/100 ml. Cul¬ ture showed no growth in 48 hours. There was intermittent drainage of serosanguineous fluid from the nose from which hemolytic Staphylococcus aureus, a-hemolytic Streptococcus, and Neisseria catarrhalis grew on culture. The patient was treated intravenously with ampicillin so¬ dium. He remained afebrile and began to recover from his lethargy and meningism. After 24 hours, CSF rhinorrhea ceased, but air continued to fill the cerebral ventricles. On Jan 9, 1973, a bifrontal craniotomy was performed, disclosing a large defect in the dura on the right side, just above the cribriform plate. A portion of softened brain tissue extended downward, funnel¬ like, into the region of the cribriform plate. This portion of the brain was surgically re¬ tracted and the durai defect sutured. On the seventh postoperative day, a skull xray film showed complete clearing of the traumatic pneumocephalus. Four months after enucleation, an ocular prosthesis was fitted. The patient has remained free of neurological signs and symptoms for more than 18 months.
Fig 1.—Intracerebral and intraventricular pneumocephalus. Lateral (left) and frontal (right) skull roentgenograms taken two weeks following orbital fracture demonstrate air filling both lat¬ eral ventricles and third ventricle (t). Pear-shaped intracerebral pneumocephalus (black arrowheads) of right frontal lobe con¬ nects cribriform plate above nasal cavity (white arrowhead) to an¬ terior horn of lateral ventricle. Orbital fracture and ruptured globe occurred on left, while intracerebral pneumocephalus occurred on
right. COMMENT Previous Literature
There
many synonyms for pneumocephalus: cranial aerocele, pneumatocele, intracranial air pocket, are
pneumatocephalus, pneumocephalon,
cerebral
pneumocyst,
pneumoven-
the first
comprehensive report pneumocephalus. Markham44
viewed the literature up to 1967 and tabulated the findings of 295 cases. North,4- in 1971, added 41 cases of
posttraumatic pneumocephalus.
tricle, pneumocranium, pneumocele, and spontaneous ventriculogram.
Jelsma and Morre" credit Lecat7 for the first report of pneumocephalus. Chiari5 first demonstrated a mecha¬ nism of pneumocephalus formation when he found at autopsy an ethmoid sinus fracture associated with a durai tear that produced a pocket of air in the frontal lobe and air in the lateral ventricle. Luckett" published the first radio¬ logical description of pneumocephalus in a man who was struck by a trolley whose initial roentgenograms showed no intracranial air. After sneezing, he developed severe headaches and CSF rhinorrhea. Roentgenograms demon¬ strated a pneumocephalus that was confirmed at autopsy as coming from a fracture of the orbital roof, with a durai tear and a laceration of the frontal lobe that communicated with the lateral ventricle. Dandy1" made
on re¬
of
Pathogenesis Pneumocephalus
Fracture of the wall of a paranasal sinus allows the escape of air into ad¬ jacent tissue. Fractures of the medial orbital wall, involving the ethmoid si¬ nuses, are often associated with orbi¬ tal emphysema.4 Fracture of the an¬ terior wall of the frontal sinus may result in subperiosteal emphysema (extracranial pneumatocele)." Frac¬ tures of the inner wall of the frontal ethmoid, sphenoid, or mastoid sinus may allow air to pass intracranially, '"
forming
a
pneumocephalus.
Orbital roof fractures from blunt or
trauma are likely to be associated with pneumocephalus for three reasons4446: 1. The orbital plate of the frontal bone is thin and easily fractured. In blunt injury, orbital roof fracture may be associated with nasal trauma
penetrating
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in which the perpendicular plate of the ethmoid is forced upward, frac¬ turing the cribriform plate with re¬ sultant continuity between the nasal and intracranial cavity.5 2. The orbital roof may contain an extension of the frontal or ethmoid sinuses, so that a fracture can estab¬ lish continuity between the sinus and intracranial cavity (Fig 2). 3. The dura over the orbital roof is thin and firmly anchored by its exten¬ sions through the bone along the ol¬ factory nerves, so that roof fractures are usually associated with a durai tear. A durai tear tends to remain patent because the dura is a poorly healing tissue. In addition, brain, arachnoid, bone, or sinus mucosa may be incarcerated in the defect.47 Air passes through the durai tear by one of two mechanisms:17 (1) Ball Value—air may be forced through the durai tear during coughing, sneezing, or straining. After this pressure wave, the tear is sealed by brain or meningeal tissue, trapping the air in¬ side. Repeated instances of this could raise intracranial pressure. (2) Nega¬ tive Pressure—If a CSF leak is excès-
sive, a negative pressure may be created, sucking air in through the durai defect.
Roentgenographic Appearance of Pneumocephalus The air distributes itself intracranially along anatomic spaces, each of which has a characteristic roentgeno¬ graphic appearance (Fig 3) and pathogenic mechanism.6111218 Epidural pneumocephalus results if no durai tear is present. It is rare (7.1% of cases),41 and usually results from processes that erode the bone but not the dura. Roentgenograms demonstrate a small loculated collec¬ tion of air that does not move on change of position. Subdural pneumocephalus is more common (28.1% of cases),11 and usu¬ ally accompanies fractures or tumors of the frontobasal region that pro¬ duce a durai defect. The air moves freely, distributes itself over the hem¬ isphere, may outline the falx cerebri or tentorium, and may form an airfluid level. Subarachnoid pneumocephalus re¬ quires a tear in the arachnoid. The air often spreads through the foramina of Luschka and Magendie to the cere-
Fig 2.—Pathogenesis of pneumo¬ cephalus. Skull and black pencil dem¬ onstrate one pathway that a penetrating orbital missile could take to produce a pneumocephalus. It enters orbit in a su¬ peromedial direction, penetrates thin orbi¬ tal roof, passes through extension of fron¬ tal sinus, and enters anterior cranial fossa. bral ventricles, as is seen in a diag¬ nostic pneumoencephalogram. Subarachnoid and intraventricular air are present alone or in combination in about 20% of cases of pneu¬
mocephalus.44 Roentgenographically,
the air outlines the cortical spaces
Fig 3.—Possible locations of intracranial air: E, epidural; D, subdural; C, intracerebral; V, intraventricular; A, subarachnoid. Air may enter cranium from nasal cavity (n), frontal sinus (f), ethmoid sinuses (e), or sphenoid sinus (s).
and basal cisterns and shifts on change of position. Subarachnoid air most commonly results from commu¬ nication between the posterior eth¬ moid or sphenoid sinuses and the ba¬ sal cisterns. Intracerebral pneumocephalus oc¬ curs when the brain and dura adhere to the fracture, so that air does not spread beneath the meninges, but penetrates the brain substance directly. The air remains intracere¬ bral in about 25% of cases.14 In an ad¬ ditional 10%, a cerebral necrosis is present that allows the air to enter the ventricles, as in our patient (Fig 1). The intracerebral air pattern ex¬ tends upward from the floor of the anterior fossa or backward from the region of the frontal sinus. It has a pear or funnel shape, the narrow neck of which leads to its source. Combina¬ tions of the various locations occur in about 20% of cases.41 In our patient, the durai tear and intracerebral pneumocephalus were on the right, while the orbital frac¬ ture and ruptured globe were on the left. The probable mechanism is that a fragment of the shattered grinding wheel struck the left orbit with a force directed superomedially that drove the nasal bones up to the right, fracturing the right side of the cribri¬ form plate and lacerating the over¬ lying meninges and frontal lobe. Al¬ ternatively, a piece of the grinding wheel may have penetrated the roof of the left orbit in a superonasal di¬ rection, passing through the ethmoid or frontal sinus into the right ante¬ rior cranial fossa. The absence of an intracranial foreign body and the connection of the frontal lobe pneu¬ mocephalus to the right cribriform plate area make this mechanism un¬
likely.
Clinical Characteristics and of Pneumocephalus
Diagnosis
Pneumocephalus occurs in less than
1% of
cases
of head trauma, but is
present in about 8% of fractures in¬
the nasal sinuses.11'47 The cause of pneumo¬ cephalus is frontocranial trauma from traffic accidents or missile injuries, accounting for about 75% of cases. Other causes include osteomas of the
volving most
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common
paranasal sinuses (13%), sinusitis (9%), and surgical fistulas (4%).41
Intracranial involvement in pene¬ trating orbital injuries commonly es¬ capes early detection, as Bard and Jarrett noted in their analysis of 53 cases.14 The wound is often small and of uncertain direction. The severe ocular damage detracts attention from the intracranial injury. Roent¬ genographic studies are unreliable in detecting small associated fractures. When symptoms and signs do occur, they are often nonspecific. Headache,
meningism, stupor, or papilledema findings compatible with subdural hematoma, brain abscess, meningitis, and pneumocephalus.10 Pneumocephalus usually has a de¬ layed onset and is clinically silent. It are
is seldom
seen on
initial skull x-ray
films, and remains unsuspected until it appears
as a startling discovery subsequent roentgenograms. Pre¬ sumably, the durai defect is initially sealed by edema or a hematoma. As these resolve or as they are dislodged by sneezing or straining, air is forced
on
into the cranium. About one fourth of develop in the first week, half within the first month, and three fourths by three months after injury. Only 5% develop after one year.11 Thus, in order to detect the asympto¬ matic and delayed onset of pneu¬ mocephalus, skull roentgenograms must be repeated periodically on pa¬ tients with fractures of the paranasal sinuses. The brow-up position with a hori¬ zontal beam is most helpful, since it allows the air to collect superiorly, creating an air-fluid level.12·18 Detec¬ tion of a small pneumocephalus may require multiple head positions to demonstrate shifts of the air pattern, stereoscopic roentgenograms, and tomograms. Even in the presence of pneumocephalus and orbital injury, the most rigorous roentgenographic examination will often fail to disclose the small fracture in the frail orbital roof. Rarely, the patient will report hearing a splashing sound when he moves his head. This succussion splash can be verified by cerebral ascultation, and probably represents the movement of fluid within the air cases
cavity.11 Cerebrospinal fluid rhinorrhea and pneumocephalus have the same clini¬ cal significance: a break in the dura
with risk of intracranial infection. Observable CSF rhinorrhea accom¬ panies pneumocephalus in about 25% of cases.111217 Pneumocephalus is often a better clue in the detection of intracranial involvement, since it is present consistently, while a CSF leak is usually intermittent. A frac¬ ture or penetrating injury of the orbit that does not connect to a nasal sinus may allow CSF to leak directly into the orbit, producing lid swelling and proptosis.1719 In some of these in¬ stances, the CSF flows out of the orbi¬ tal wound (CSF orbitorrhea).'4'20-21 Treatment of Durai Fistula.—The chief aim in the treatment of orbital fractures with intracranial involve¬ ment is the prevention of meningitis and brain abscess. Pneumocephalus is merely a sign of the durai tear, and the air will be absorbed when the tear is sealed. Prompt parenteral adminis¬ tration of broad-spectrum antibiotics may prevent CNS infection. If the durai tear heals spontaneously, surgi¬ cal intervention may be avoided.1114 However, about 25% of patients with durai lacerations develop meningitis, and some surgeons advocate prompt operative repair.12·17-22 Markham11 has listed the following indications for the surgical treatment of pneumo¬ cephalus: (1) delayed healing of the durai defect, allowing persistent pneumocephalus or CSF rhinorrhea, (2) recurrence of pneumocephalus or CSF rhinorrhea, (3) neoplasm or si¬ nusitis that creates a persistent path¬ way for ingress of air, and (4) the presence of an intracerebral pneu¬ mocephalus, which implies adherence of the brain to a fistulous tract. In all cases, individual considerations and neurosurgical consultation will vary the final decision. In the presence of a known orbitosinus-cranial fistula, foreign material, such as wires and alloplastic plates, should not be used in repair of orbital fractures, because they may increase the chance of infection. Repair of the orbital damage may have to be de¬ layed until the durai fistula can be sealed.
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This investigation was supported in part by the Heed Ophthalmic Foundation (Dr. Waring). Paul L. Carmichael, MD, referred the patient. Randall W. Bell, MD, reviewed the manu¬
script.
Key Words.—Pneumocephalus; orbital fracture; meningitis; cerebrospinal fluid (CSF) rhinorrhea; aerocele; paranasal
sinus fracture.
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