Infraorbital nerve dehiscence: The anatomic cause of maxillary sinus “vacuum headache”? H. B. WHITTET, FRCS, Oxford, England
Vacuum disorders of the paranasal sinuses are well described. Patients with facial pain in the distribution of the infraorbital nerve are often labelled assufferingfrom a “vacuum maxillary sinusitis” and empirically treated by intranasal antrostomy.A variety of mechanisms have been postulated for the production of symptoms in this condition, but all ignore the fact that the maxillary sinus is a relatively insensitive structure. This article introduces a dehiscence of the bony infraorbital newe canal within the antrum as an anatomic variant and suggests that it may provide the anatomic basis for vacuum sinusitis in the presence of a small natural ostium. Definitive diagnosis is made by outpatient antroscopy, and surgical treatment takes the form of a middle or inferior meatal antrostomy. Persistent symptoms may benefit from an infraorbital neuropexy to provide added protection to the exposed nerve. (OTOLARYNGOLHEAD NECKSURG1992;10721,)
S y m p t o m s attributable to negative pressure effects within the paranasal sinuses in the absence of obvious clinical signs have been described for many years. Sluder’ described a frontal sinus headache and vacuum ethmoiditis as a result of closure of the infundibulum, which responded to intranasal ethmoidectomy and opening of the frontonasal duct. In 1914, Lynch’ introduced the concept of a vacuum disorder affecting the maxillary sinus, emphasizing the absence of a predisposing inflammatory condition. He attributed the symptoms produced to a localized hyperemia resulting from a negative pressure and showed that they could be relieved by surgical re-establishment of normal ventilation. There is a distinct clinical group of patients who manifest recurrent cheek pain, possibly associated with ipsilateral fluctuating nasal obstruction and who have no obvious associated condition to explain their symptoms. Plain sinus radiology or CT scans are reported as normal and empirically performed middle or inferior meatal antrostomies result in resolution of the presenting symptoms. Although attributed to negative pressure
From the ENT Department, Radcliffe Infirmary, Oxford. Presented at the Annual Meeting of the American Academy of Otolaryngology-Head and Neck Surgery, New Orleans, La., Sept. 24-28, 1989. Received for publication Feb. 19, 1991; revision received Feb. 10, 1992; accepted March 5 , 1992. Reprint requests: H. B. Whittet, FRCS, Department of ENT, Radcliffe Infirmary, Woodstock Road, Oxford, OX2 6HE, England. 231 1I37643
effects, the precise mechanism of action has not been clearly elucidated. Anatomic Note
The infraorbital nerve is a purely sensory nerve that traverses the antral roof, usually completely encased in a bony canal, to emerge at the infraorbital foramen. It usually consists of two or four fasciculi, together with the infraorbital branch of the maxillary artery, which runs along the undersurface of the nerve and less frequently medial or lateral.’ The floor of the orbit is thin and may be defective over a variable extent, which may predispose to clinical effect^.^ The thickness of the antral roof varies with age and degree of pneumatization of the maxillary sinus, being thinner medially than laterally. The inferior (antral) wall of the infraorbital canal is particularly thin, with an average thickness of 0.2 mm and an incidence of complete dehiscence between 12% and 16% in dried skull specimens.’ The infraorbital nerve has a number of branches within the antrum’ that supply the upper dentition, antral mucosa, and, to a variable extent, the lateral wall and floor of the nasal cavity. As it emerges at the infraorbital foramen, it divides into ten or more terminal nasal, palpebral, and labial branches. METHODS AND RESULTS Clinical Endoscopic/Antroscopic Assessment
As part of a nasal endoscopy and antroscopy clinic, 300 antroscopic procedures were performed over a 2year period. A sublabial approach was used to achieve good visualization of the ostium and antral contents. In
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
21
OtolaryngologyHead and Neck Surgery
Fig. 1. Endoscopic view of a left infraorbital nerve shows dehiscent portion anteriorly (dn), a bony portion posteriorly (bn), and a visible infraorbitol artery (a).
Fig. 2. A prominent bony infraorbital neive indenting the antral roof. A identifies anterior. Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Volume 107 Number 1
infraorbitai newe dehiscence
July 1992
Fig. 3. Right ontrum.View of A, a dehiscent nerve and small ostium, and B, a bony prominent newe canal with a large ostium. o identifies the ostium; o identifies the infraorbitai artery; and the arrow identifies the infraorbital nerve. Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
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OfolaryngologyHead and Neck Surgery
24 WHITET
Fig. 4. Contact hemorrhagic ‘spor (arrow)that resultedfrom direct probing of an exposed infraorbital newe during endoscopic assessment.
12 cases the antral appearances were otherwise normal, but there was an obvious submucosal dehiscence of the infraorbital nerve on the antral roof, as shown in Fig. 1, in which the infraorbital artery may clearly be seen accompanying the nerve on its undersurface. The course of the nerve may often be seen as a bony prominence within the antrum (Fig. 2). In this study, 35 antra displayed such a bony prominence. It was noted that six cases of the submucosally dehiscent infraorbital nerve manifested symptoms of facial pain in the peripheral distribution of the infraorbital nerve. One of the cases had been diagnosed as experiencing an ‘atypical trigeminal neuralgia.’ This symptomatic groupwithout exception-demonstrated an extremely small natural maxillary ostium on the affected side in association with the submucosally exposed nerve (Fig. 3, a). In contrast, the remaining six cases of submucosally dehiscent infraorbital nerve in patients who were asymptomatic possessed an unusually widely patent maxillary sinus ostium (Fig. 3, b). Local manipulation of the nerve using a silver probe, as shown by the localized spots of contact hemorrhage in Fig. 4, reproduced the presenting symptoms. Locally
applied anesthetic spray subsequently abolished any response to further stimulation. These responses were demonstrated by both the symptoinatic and asyinptomatic cases of subrnucosal dehiscence. Seventy antra exhibited small or vestigial ostia, with no dehiscence of the infraorbital nerve canal and no associated symptoms of facial pain. Cadaver Study
These observations prompted a study of cadavers to further investigate the incidence of infraorbital nerve canal dehiscence and associated vestigiality of the sinus ostium. One hundred five antra were examined from subjects with an age range from 5 1 to 76 years. Sixteen (15%) of these subjects exhibited a submucosal dehiscence of the infraorbital nerve, and of these 16 cases, nine also showed a vestigial or very small natural ostium. Histologic Assessmenf
There is a clear difference in the protective cover that separates antral mucosa from nerve bundles between the bone-covered and submucosally dehiscent
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Volume 107 Number 1 July 1992
lnfraorbitai nerve dehiscence 25
Fig. 5. Histologic specimens of A, an intact bony infraorbital newe canal and B, a dehiscent nerve show the close approximation between mucosa and nerve in the latter (thin arrow). m identifies antral rnucosa; b identifies bone; n identifies infraorbital nerve fasciculi. Dehiscent bone is indicated by the bold orrows (Hematoxyiin-eosinstain; original magnification x 420.)
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
OtolaryngologyHead and Neck Surgery
26 WHllTET
mucosal inflammation or mechanical trauma. In contrast to the facial nerve within the middle ear, the infraorbital nerve is a purely sensory nerve that is especially vulnerable to both pressure and the effects of local anesthesia. MANAGEMENT Clinical History
The patients who manifested facial pain as a result of an infraorbital nerve dehiscence experienced pain confined to the peripheral distribution of that nerve. The pain could be localized directly to the point of emergence of the nerve at the infraorbital nerve foramen. The pain was described as a dull, nagging pain that was made more obvious during upper respiratory tract infections or when the ipsilateral nasal airway'was obstructed. These patients frequently had been referred for a neurologic 'assessment or had been diagnosed as experiencing atypical facial pain. Radiologic Investigation
Plain sinus radiology is not helpful in identification of a dehiscent infraorbital nerve canal, but coronal tomography may be of more value.6 Computerized axial tomography (CT) scanning can demonstrate very clearly the course of the nerve on coronal sections, as shown in this patient, who also demonstrated concomitant ethmoid mucosal disease (Fig. 6, A ) . Nasal EndoscopyI Antroscopy
Fig. 6. A, Coronal CT scan and B, antroscopic view of an abnormally coursing infraorbital nerve. x identifies infraorbital nerve in the scan; o identifies the natural ostium.
nerve. In Fig. 5, A , the ciliated epithelium of the antral mucosa is seen to be clearly separated from the nerve by an intact layer of bone. Figure 5 , B , by way of contrast, illustrates the intimate relationship between the nerve bundles of a partially dehiscent nerve and the antral mucosa, and shows how vulnerable it may be to
Radiology may allow a noninvasive assessment of infraorbital nerve dehiscence, but the definitive diagnostic technique is antroscopy-preferably under local anaesthesia. This allows direct manipulation of the exposed nerve to reproduce the presenting symptoms. Figure 6, B shows the endoscopic appearance of Fig. 6, A , showing an aberrantly coursing infraorbital nerve traversing the midpoint of the antrum. It is easy to see how this structure could be inadvertently damaged during a radical antrostomy such as the Caldwell-Luc procedure. A dehiscent nerve is even potentially at risk when a middle meatal antrostomy is performed, if it lies close to the natural ostium. In such procedures there is much to be said for performing a preliminary antroscopy to exclude such an anatomic variant. Surgical Management
All six patients with a diagnosis of infraorbital nerve dehiscence had an initial attempt at surgical cure by the performance of either inferior meatal or middle meatal antrostomies. Four of these had immediate and complete resolution of their symptoms, although they ex-
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Volume 107 Number 1 Juty 1992
lnfraorbital nerve dehiscence 27
A Fig. 7, A and 6. Diagrammatic representations of infraorbital neuropexy. M identifies antral mucosa;
N identifies infraorbital nerve; and F identifies subdermal fat graft (see arrows in B).
perienced a mild recurrence of their symptoms during upper respiratory tract infections, presumably as a result of mucosal inflammation directly stimulating the nerve. The remaining two patients had only temporary improvement of their symptoms. These two subjects subsequently underwent a procedure termed an infraorbital neurapexy to good effect. All six subjects remained symptom-free 12 months after their procedures. lnfraorbital Neuropexy
This procedure was developed to provide additional protection for the otherwise exposed infraorbital nerve. A subdermal fat graft harvested from the abdominal or postauricular skin is placed between the mucosa of the antrum and the infraorbital nerve by a sublabial approach. After identification of the infraorbital nerve at the infraorbital nerve foramen, the bone of the anterior maxillary wall is thinned to expose the antral mucosa and separate it from the infraorbital nerve. The subdermal or temporalis fascia1 graft is then positioned between the mucosa and nerve (Fig. 7, A and B ) . DISCUSSION
Both Sluder' and Lynch' have described the clinical features associated with vacuum disorders of the frontal, ethmoid, and maxillary sinuses. Vacuum disorders have a precedent in other areas, notably the middle ear, where eustachian tube dysfunction can lead to tympanic membrane changes .' McMurray' observed negative pressure fluctuations within the antrum with respiration
and noted that increasing ostial size minimized these fluctuations. Other workers have described significant pressure changes within the paranasal sinuses and have attributed them to a variety of causes, such as ciliary displacement of mucous plugs and gas absorption within sealed Extensive studies of ostial size and patency within the antrum have clearly shown that negative pressure changes occur when the ostial diameter falls below a critical level.'0~''~'2 Although such changes are demonstrable, the mechanism of action for pain production is not so obvious. Wolff13 demonstrated by an elegant series of experiments that the antral mucosal lining is relatively insensitive to touch, although he made no reference to the antral roof or infraorbital nerve. Lynch' suggested that local hyperemia resulting from the negative pressure was the cause of symptoms. Indeed. later workers14 have implicated vasodilatation of antral mucosal blood vessels as a cause of the positional discomfort that may occur with maxillary ostial occlusion. Recent work" has shown substance-P-containing nerve fibers within the nasal mucosa. This is a polypeptide that acts as a pain mediator and has been implicated as a cause of ethmoid pain as a result of mucosal contact in the middle meatus.I6 This may be a possible mechanism in vacuum sinusitis, with the stimulus being pressure change rather than an active disease process. A dehiscent or prominent infraorbital nerve is vul-
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
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OtolaryngologyHead and Neck Surgery
WHIllET
nerable to direct mechanical trauma. This may explain the incidence of postoperative infraorbital anaesthesia, paraesthesia, and neuralgia encountered after a radical antrostomy, such as the Caldwell-Luc operation, rather than by retractor pressure on the emerging nerve. CONCLUSIONS
A submucosal dehiscence of the infraorbital nerve within its antral course is an anatomic variant that may be symptomatic when associated with a poorly developed natural ostium in the otherwise insensitive maxillary sinus. The precise mechanism for this is as yet speculative, but could be the result of a negative pressure effect from the small size of the natural ostium and subsequent release of local pain mediators, such as substance-P. The diagnosis is made endoscopically under local anesthesia combined with CT scanning to exclude concomitant paranasal sinus disease. An intranasal antrostomy may provide relief, but for persistent symptoms an infraorbital neuropexy may be performed. This anatomic variant seems to provide a satisfactory explanation for the condition of vacuum maxillary sinusitis, although further work is necessary to identify the presence of pain mediators within the antral mucosa. REFERENCES
Sluder G. Nasal neurology, headaches and eye disorders. London: Henry Kimpton, 1927:31-67. Lynch RC. Vacuum diseases of the maxillary sinus. Ann Otol Rhinol Laryngol 1914;3:59-66. Lang J . Clinical anatomy of the head. Berlin: Springer-Verlag, 1983:38-472.
4. Whittet HB, McGlashan J, Croft CB. Noninfective orbital complications resulting from natural defects of the antral roof. ORL J Otorhinolaryngol Relat Spec 1990:52:196-201. 5 Last RJ. Anatomy regional and applied. 6th ed. Edinburgh: Churchill Livingstone, 1978:403-35. 6 Croft CB, Whittet HB, Fisher EW, et al. Polytomographic radiology in the diagnosis and management of maxillary antral disease as determined by antroscopy. Clin Otolaryngol 1991;l6:70-S. 7 McMurray J. The intra-antral air pressure incident to the respiratory excursion and its effect on antral drainage. Arch Laryngol I931 :8:581-5. 8 Hilding AC. Production of negative pressure in the respiratory tract by ciliary action and its relation to postoperative atelectasis. Anesthesiology 1944;5:225-36. 9 Loring SH, Tenney SM. Gas absorption from frontal sinuses. Arch Otolaryngol 1973;97:470-4. 10 Drettner B . Pathophysiology of paranasal sinuses with clinical implications. Clin Otolaryngol 1980;5:277-84. 11. Kortekangas AE. Patency and resistance tests of the maxillary ostium. Rhinology 1976;14:41-2. 12 Aust R. Measurements of the ostial sire and oxygen tension in the maxillary sinus. Rhinology 1976;14:43-4. 13 Wolff HG. Headache mechanisms. Int Arch Allergy Appl Immunol 1955;7:210-25. 14. Falck B. Svanholm H, Aust R, Backlund L. The relationship between body posture and pressure in occluded maxillary sinus of man. Rhinology 1989:27:161-7. 15 Uddman R, Malm L, Sundler F. Substance P containing nerve fibers in the nasal mucosa. Arch Otorhinolaryngol 1983;238:916. 16 Stammberger H, Wolf G . Headaches and sinus disease: the endoscopic approach. Ann Otol Rhinol Laryngol 1988;97(Suppl 134):3-23.
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Vacuum disorders of the paranasal sinuses are well described. Patients with facial pain in the distribution of the infraorbital nerve are often labelled assufferingfrom a “vacuum maxillary sinusitis” and empirically treated by intranasal antrostomy.A variety of mechanisms have been postulated for the production of symptoms in this condition, but all ignore the fact that the maxillary sinus is a relatively insensitive structure. This article introduces a dehiscence of the bony infraorbital newe canal within the antrum as an anatomic variant and suggests that it may provide the anatomic basis for vacuum sinusitis in the presence of a small natural ostium. Definitive diagnosis is made by outpatient antroscopy, and surgical treatment takes the form of a middle or inferior meatal antrostomy. Persistent symptoms may benefit from an infraorbital neuropexy to provide added protection to the exposed nerve. (OTOLARYNGOLHEAD NECKSURG1992;10721,)
S y m p t o m s attributable to negative pressure effects within the paranasal sinuses in the absence of obvious clinical signs have been described for many years. Sluder’ described a frontal sinus headache and vacuum ethmoiditis as a result of closure of the infundibulum, which responded to intranasal ethmoidectomy and opening of the frontonasal duct. In 1914, Lynch’ introduced the concept of a vacuum disorder affecting the maxillary sinus, emphasizing the absence of a predisposing inflammatory condition. He attributed the symptoms produced to a localized hyperemia resulting from a negative pressure and showed that they could be relieved by surgical re-establishment of normal ventilation. There is a distinct clinical group of patients who manifest recurrent cheek pain, possibly associated with ipsilateral fluctuating nasal obstruction and who have no obvious associated condition to explain their symptoms. Plain sinus radiology or CT scans are reported as normal and empirically performed middle or inferior meatal antrostomies result in resolution of the presenting symptoms. Although attributed to negative pressure
From the ENT Department, Radcliffe Infirmary, Oxford. Presented at the Annual Meeting of the American Academy of Otolaryngology-Head and Neck Surgery, New Orleans, La., Sept. 24-28, 1989. Received for publication Feb. 19, 1991; revision received Feb. 10, 1992; accepted March 5 , 1992. Reprint requests: H. B. Whittet, FRCS, Department of ENT, Radcliffe Infirmary, Woodstock Road, Oxford, OX2 6HE, England. 231 1I37643
effects, the precise mechanism of action has not been clearly elucidated. Anatomic Note
The infraorbital nerve is a purely sensory nerve that traverses the antral roof, usually completely encased in a bony canal, to emerge at the infraorbital foramen. It usually consists of two or four fasciculi, together with the infraorbital branch of the maxillary artery, which runs along the undersurface of the nerve and less frequently medial or lateral.’ The floor of the orbit is thin and may be defective over a variable extent, which may predispose to clinical effect^.^ The thickness of the antral roof varies with age and degree of pneumatization of the maxillary sinus, being thinner medially than laterally. The inferior (antral) wall of the infraorbital canal is particularly thin, with an average thickness of 0.2 mm and an incidence of complete dehiscence between 12% and 16% in dried skull specimens.’ The infraorbital nerve has a number of branches within the antrum’ that supply the upper dentition, antral mucosa, and, to a variable extent, the lateral wall and floor of the nasal cavity. As it emerges at the infraorbital foramen, it divides into ten or more terminal nasal, palpebral, and labial branches. METHODS AND RESULTS Clinical Endoscopic/Antroscopic Assessment
As part of a nasal endoscopy and antroscopy clinic, 300 antroscopic procedures were performed over a 2year period. A sublabial approach was used to achieve good visualization of the ostium and antral contents. In
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
21
OtolaryngologyHead and Neck Surgery
Fig. 1. Endoscopic view of a left infraorbital nerve shows dehiscent portion anteriorly (dn), a bony portion posteriorly (bn), and a visible infraorbitol artery (a).
Fig. 2. A prominent bony infraorbital neive indenting the antral roof. A identifies anterior. Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Volume 107 Number 1
infraorbitai newe dehiscence
July 1992
Fig. 3. Right ontrum.View of A, a dehiscent nerve and small ostium, and B, a bony prominent newe canal with a large ostium. o identifies the ostium; o identifies the infraorbitai artery; and the arrow identifies the infraorbital nerve. Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
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OfolaryngologyHead and Neck Surgery
24 WHITET
Fig. 4. Contact hemorrhagic ‘spor (arrow)that resultedfrom direct probing of an exposed infraorbital newe during endoscopic assessment.
12 cases the antral appearances were otherwise normal, but there was an obvious submucosal dehiscence of the infraorbital nerve on the antral roof, as shown in Fig. 1, in which the infraorbital artery may clearly be seen accompanying the nerve on its undersurface. The course of the nerve may often be seen as a bony prominence within the antrum (Fig. 2). In this study, 35 antra displayed such a bony prominence. It was noted that six cases of the submucosally dehiscent infraorbital nerve manifested symptoms of facial pain in the peripheral distribution of the infraorbital nerve. One of the cases had been diagnosed as experiencing an ‘atypical trigeminal neuralgia.’ This symptomatic groupwithout exception-demonstrated an extremely small natural maxillary ostium on the affected side in association with the submucosally exposed nerve (Fig. 3, a). In contrast, the remaining six cases of submucosally dehiscent infraorbital nerve in patients who were asymptomatic possessed an unusually widely patent maxillary sinus ostium (Fig. 3, b). Local manipulation of the nerve using a silver probe, as shown by the localized spots of contact hemorrhage in Fig. 4, reproduced the presenting symptoms. Locally
applied anesthetic spray subsequently abolished any response to further stimulation. These responses were demonstrated by both the symptoinatic and asyinptomatic cases of subrnucosal dehiscence. Seventy antra exhibited small or vestigial ostia, with no dehiscence of the infraorbital nerve canal and no associated symptoms of facial pain. Cadaver Study
These observations prompted a study of cadavers to further investigate the incidence of infraorbital nerve canal dehiscence and associated vestigiality of the sinus ostium. One hundred five antra were examined from subjects with an age range from 5 1 to 76 years. Sixteen (15%) of these subjects exhibited a submucosal dehiscence of the infraorbital nerve, and of these 16 cases, nine also showed a vestigial or very small natural ostium. Histologic Assessmenf
There is a clear difference in the protective cover that separates antral mucosa from nerve bundles between the bone-covered and submucosally dehiscent
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Volume 107 Number 1 July 1992
lnfraorbitai nerve dehiscence 25
Fig. 5. Histologic specimens of A, an intact bony infraorbital newe canal and B, a dehiscent nerve show the close approximation between mucosa and nerve in the latter (thin arrow). m identifies antral rnucosa; b identifies bone; n identifies infraorbital nerve fasciculi. Dehiscent bone is indicated by the bold orrows (Hematoxyiin-eosinstain; original magnification x 420.)
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
OtolaryngologyHead and Neck Surgery
26 WHllTET
mucosal inflammation or mechanical trauma. In contrast to the facial nerve within the middle ear, the infraorbital nerve is a purely sensory nerve that is especially vulnerable to both pressure and the effects of local anesthesia. MANAGEMENT Clinical History
The patients who manifested facial pain as a result of an infraorbital nerve dehiscence experienced pain confined to the peripheral distribution of that nerve. The pain could be localized directly to the point of emergence of the nerve at the infraorbital nerve foramen. The pain was described as a dull, nagging pain that was made more obvious during upper respiratory tract infections or when the ipsilateral nasal airway'was obstructed. These patients frequently had been referred for a neurologic 'assessment or had been diagnosed as experiencing atypical facial pain. Radiologic Investigation
Plain sinus radiology is not helpful in identification of a dehiscent infraorbital nerve canal, but coronal tomography may be of more value.6 Computerized axial tomography (CT) scanning can demonstrate very clearly the course of the nerve on coronal sections, as shown in this patient, who also demonstrated concomitant ethmoid mucosal disease (Fig. 6, A ) . Nasal EndoscopyI Antroscopy
Fig. 6. A, Coronal CT scan and B, antroscopic view of an abnormally coursing infraorbital nerve. x identifies infraorbital nerve in the scan; o identifies the natural ostium.
nerve. In Fig. 5, A , the ciliated epithelium of the antral mucosa is seen to be clearly separated from the nerve by an intact layer of bone. Figure 5 , B , by way of contrast, illustrates the intimate relationship between the nerve bundles of a partially dehiscent nerve and the antral mucosa, and shows how vulnerable it may be to
Radiology may allow a noninvasive assessment of infraorbital nerve dehiscence, but the definitive diagnostic technique is antroscopy-preferably under local anaesthesia. This allows direct manipulation of the exposed nerve to reproduce the presenting symptoms. Figure 6, B shows the endoscopic appearance of Fig. 6, A , showing an aberrantly coursing infraorbital nerve traversing the midpoint of the antrum. It is easy to see how this structure could be inadvertently damaged during a radical antrostomy such as the Caldwell-Luc procedure. A dehiscent nerve is even potentially at risk when a middle meatal antrostomy is performed, if it lies close to the natural ostium. In such procedures there is much to be said for performing a preliminary antroscopy to exclude such an anatomic variant. Surgical Management
All six patients with a diagnosis of infraorbital nerve dehiscence had an initial attempt at surgical cure by the performance of either inferior meatal or middle meatal antrostomies. Four of these had immediate and complete resolution of their symptoms, although they ex-
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
Volume 107 Number 1 Juty 1992
lnfraorbital nerve dehiscence 27
A Fig. 7, A and 6. Diagrammatic representations of infraorbital neuropexy. M identifies antral mucosa;
N identifies infraorbital nerve; and F identifies subdermal fat graft (see arrows in B).
perienced a mild recurrence of their symptoms during upper respiratory tract infections, presumably as a result of mucosal inflammation directly stimulating the nerve. The remaining two patients had only temporary improvement of their symptoms. These two subjects subsequently underwent a procedure termed an infraorbital neurapexy to good effect. All six subjects remained symptom-free 12 months after their procedures. lnfraorbital Neuropexy
This procedure was developed to provide additional protection for the otherwise exposed infraorbital nerve. A subdermal fat graft harvested from the abdominal or postauricular skin is placed between the mucosa of the antrum and the infraorbital nerve by a sublabial approach. After identification of the infraorbital nerve at the infraorbital nerve foramen, the bone of the anterior maxillary wall is thinned to expose the antral mucosa and separate it from the infraorbital nerve. The subdermal or temporalis fascia1 graft is then positioned between the mucosa and nerve (Fig. 7, A and B ) . DISCUSSION
Both Sluder' and Lynch' have described the clinical features associated with vacuum disorders of the frontal, ethmoid, and maxillary sinuses. Vacuum disorders have a precedent in other areas, notably the middle ear, where eustachian tube dysfunction can lead to tympanic membrane changes .' McMurray' observed negative pressure fluctuations within the antrum with respiration
and noted that increasing ostial size minimized these fluctuations. Other workers have described significant pressure changes within the paranasal sinuses and have attributed them to a variety of causes, such as ciliary displacement of mucous plugs and gas absorption within sealed Extensive studies of ostial size and patency within the antrum have clearly shown that negative pressure changes occur when the ostial diameter falls below a critical level.'0~''~'2 Although such changes are demonstrable, the mechanism of action for pain production is not so obvious. Wolff13 demonstrated by an elegant series of experiments that the antral mucosal lining is relatively insensitive to touch, although he made no reference to the antral roof or infraorbital nerve. Lynch' suggested that local hyperemia resulting from the negative pressure was the cause of symptoms. Indeed. later workers14 have implicated vasodilatation of antral mucosal blood vessels as a cause of the positional discomfort that may occur with maxillary ostial occlusion. Recent work" has shown substance-P-containing nerve fibers within the nasal mucosa. This is a polypeptide that acts as a pain mediator and has been implicated as a cause of ethmoid pain as a result of mucosal contact in the middle meatus.I6 This may be a possible mechanism in vacuum sinusitis, with the stimulus being pressure change rather than an active disease process. A dehiscent or prominent infraorbital nerve is vul-
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
28
OtolaryngologyHead and Neck Surgery
WHIllET
nerable to direct mechanical trauma. This may explain the incidence of postoperative infraorbital anaesthesia, paraesthesia, and neuralgia encountered after a radical antrostomy, such as the Caldwell-Luc operation, rather than by retractor pressure on the emerging nerve. CONCLUSIONS
A submucosal dehiscence of the infraorbital nerve within its antral course is an anatomic variant that may be symptomatic when associated with a poorly developed natural ostium in the otherwise insensitive maxillary sinus. The precise mechanism for this is as yet speculative, but could be the result of a negative pressure effect from the small size of the natural ostium and subsequent release of local pain mediators, such as substance-P. The diagnosis is made endoscopically under local anesthesia combined with CT scanning to exclude concomitant paranasal sinus disease. An intranasal antrostomy may provide relief, but for persistent symptoms an infraorbital neuropexy may be performed. This anatomic variant seems to provide a satisfactory explanation for the condition of vacuum maxillary sinusitis, although further work is necessary to identify the presence of pain mediators within the antral mucosa. REFERENCES
Sluder G. Nasal neurology, headaches and eye disorders. London: Henry Kimpton, 1927:31-67. Lynch RC. Vacuum diseases of the maxillary sinus. Ann Otol Rhinol Laryngol 1914;3:59-66. Lang J . Clinical anatomy of the head. Berlin: Springer-Verlag, 1983:38-472.
4. Whittet HB, McGlashan J, Croft CB. Noninfective orbital complications resulting from natural defects of the antral roof. ORL J Otorhinolaryngol Relat Spec 1990:52:196-201. 5 Last RJ. Anatomy regional and applied. 6th ed. Edinburgh: Churchill Livingstone, 1978:403-35. 6 Croft CB, Whittet HB, Fisher EW, et al. Polytomographic radiology in the diagnosis and management of maxillary antral disease as determined by antroscopy. Clin Otolaryngol 1991;l6:70-S. 7 McMurray J. The intra-antral air pressure incident to the respiratory excursion and its effect on antral drainage. Arch Laryngol I931 :8:581-5. 8 Hilding AC. Production of negative pressure in the respiratory tract by ciliary action and its relation to postoperative atelectasis. Anesthesiology 1944;5:225-36. 9 Loring SH, Tenney SM. Gas absorption from frontal sinuses. Arch Otolaryngol 1973;97:470-4. 10 Drettner B . Pathophysiology of paranasal sinuses with clinical implications. Clin Otolaryngol 1980;5:277-84. 11. Kortekangas AE. Patency and resistance tests of the maxillary ostium. Rhinology 1976;14:41-2. 12 Aust R. Measurements of the ostial sire and oxygen tension in the maxillary sinus. Rhinology 1976;14:43-4. 13 Wolff HG. Headache mechanisms. Int Arch Allergy Appl Immunol 1955;7:210-25. 14. Falck B. Svanholm H, Aust R, Backlund L. The relationship between body posture and pressure in occluded maxillary sinus of man. Rhinology 1989:27:161-7. 15 Uddman R, Malm L, Sundler F. Substance P containing nerve fibers in the nasal mucosa. Arch Otorhinolaryngol 1983;238:916. 16 Stammberger H, Wolf G . Headaches and sinus disease: the endoscopic approach. Ann Otol Rhinol Laryngol 1988;97(Suppl 134):3-23.
Downloaded from oto.sagepub.com at UCSF LIBRARY & CKM on February 19, 2015
