Ann 0101 Rhinol Laryngol99: 1990
PATHOLOGIC FINDINGS IN THE LABYRINTHINE SEGMENT OF THE FACIAL NERVE IN A CASE OF FACIAL PARALYSIS C. GARY JACKSON, MD
GLENN D. JOHNSON,
NASHVILLE, TENNESSEE
VINCENT J. HYAMS, WASHINGTON,
MD
HANOVER, NEW HAMPSHIRE
MD
DENNIS
DC
S. POE, MD
BURLINGTON, MASSACHUSETTS
The histopathologic findings for a patient with acute facial paralysis caused by herpes zoster oticus who obtained no return of active facial function after 1 year are presented. All imaging studies were nondiagnostic. Biopsy of the labyrinthine segment was performed. Histopathologic analysis showed a sharp line of demarcation between sclerotic nerve proximal to and necrotic nerve distal to the meatal foramen area of the fallopian canal. This finding is consistent with observations that the lesion producing Bell's palsy and herpes zoster oticus usually is situated at the meatal foramen. KEY WORDS -
facial paralysis, herpes zoster oticus.
INTRODUCTION
pression is initiated at or confined to the labyrinthine segment by use of a middle fossa approach.
The major controversy today in the management of the patient with idiopathic acute peripheral facial palsy is whether patients with poor prognostic tests should undergo surgical decompression of the facial nerve. Since 85 % of patients with Bell's palsy will experience a satisfactory return of facial function with no treatment, I electrodiagnostic tests are used to identify those patients with extensive degeneration and a high probability for poor functional return. Fisch" has recommended decompression when degeneration reaches 90 % to 94 % by electroneurography within 3 weeks of onset of paralysis. Intraoperative evoked electromyography (EMG) has shown that the lesion producing Bell's palsy is located at the meatal foramen of the fallopian canal in 94 % of patients." Therefore, decom-
The location of the lesion in Bell's palsy at the meatal foramen (the entrance of the fallopian canal at the fundus of the internal auditory canal) is consistent with the known anatomy of this region. The loosely arranged intrameatal fibers of the facial nerve are constricted in the meatal foramen to form a fibrous ligament. 2 The meatal foramen is approximately 0.61 mm in diameter" and is the narrowest portion of the fallopian canal. Fisch" has referred to this area as a "physiologic bottleneck," in which the facial nerve fibers are literally strangulated in the presence of inflammatory edema. The facial paralysis associated with herpes zoster oticus has, in general, a worse prognosis than that
Labyrinthine section of facial nerve. A) Schematic of middle fossa exposure. Shaded area - biopsied segment of facial nerve. B) Facial nerve at point of constriction in meatal foramen of fallopian canal (H & E, original x400). Left side of photograph shows essentially normal nerve, with sharp demarcation from necrotic, fibrotic anuclear nerve fragment on right. From The Otology Group. Nashville, Tennessee (jackson, Johnson, Poe), and the Armed Forces Institute of Pathology, Washington, DC (Hyams). REPRINTS - C. Gary Jackson, MD, The Otology Group, 1811 State St, Nashville, TN 37203.
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Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
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Jackson et al, Labyrinthine Segment of Facial Nerve
caused by Bell's palsy.' Although the cause of the edema is different in these two conditions, the location of the nerve conductivity block, as measured by intraoperative evoked EMG, is the same, ie, the meatal foramen. 4 This localization has been explained by both anatomic and electrophysiologic studies, but there has been no histopathologic confirmation. A case of a patient with herpes zoster oticus that resulted in a poor return of function is presented. Biopsy of the labyrinthine segment of the facial nerve demonstrated a sharp demarcation between sclerotic and necrotic nerve at the meatal foramen. CASE REPORT
The patient is a 33-year-old woman who developed an acute, complete left facial palsy accompanied by ear pain, aural vesicles, and dizziness. She had no hearing loss. Her facial paralysis persisted without improvement for 6 months, when facial nerve stimulation testing elicited no response on the left at 6.5 rn A. The nerve appeared normal on transmastoid facial nerve decompression, but no return of function was observed after 6 months. She was referred to The Otology Group, PC, where 1 year after the onset of paralysis she exhibited a complete left facial paralysis. There was no response on the left to maximal stimulation electrical testing. Electromyography indicated total denervation of facial musculature with no signs of regeneration. Results of audiometry and auditory brain stem response testing were normal. Highresolution computed tomograms of the temporal bone and magnetic resonance images of the posterior fossa and intratemporal facial nerve were normal except for changes from the transmastoid decompression. The lack of facial nerve function after 1 year demanded exploration of the facial nerve despite nondiagnostic imaging studies. When the labyrinthine and internal auditory canal segments of the facial nerve were explored through a middle fossa approach, the intratympanic and internal auditory canal segments of the nerve appeared normal. However, the labyrinthine segment had the appearance of devitalized nerve. A biopsy sample of the labyrinthine segment was taken (see Figure, A), and there was no evidence of tumor on frozen section. A hypoglossal-facial nerve anastomosis then was performed. HISTOPATHOLOGY
The permanent hematoxylin and eosin-stained histologic sections from the facial nerve biopsy sample (labyrinthine section at the meatal foramen of the fallopian canal) showed a sharp demarcation of the proximal portion of the nerve, in which there was essentially normal histology except for a slight
sclerotic appearance. Schwann cells and perineural connective tissue were prominent in the normal nerve section and were differentiated from the distal nerve portion, in which there was a mixed fibrotic and necrotic anuclear micromorphology. There were scattered collections of small, round inflammatory cells within the distal necrotic nerve segment (see Figure, B). DISCUSSION
Most of the histopathologic findings reported with Bell's palsy and herpes zoster oticus are the result of postmortem studies. May et al' note that degeneration, hemorrhage, and inflammatory infiltrates are present in the facial nerves of patients who had idiopathic palsy and herpes zoster oticus, Fowler" described the findings for the facial nerve of a patient 14 days after onset of paralysis who had chronaxie studies indicating complete degeneration of all muscles supplied by the paralyzed facial nerve. There were fresh hemorrhages in the internal auditory canal between the region of Scarpa's ganglion and the narrow bony channel of the porus acousticus. Also noted in this region were neural sheaths that looked swollen and empty. It is difficult to interpret the significance of these researchers' findings, since there is great variability in the duration between onset of facial paralysis and death and in the severity of paralysis. There are very few reports in which degree of palsy and results of prognostic tests are available.' We are unaware of any reports of the histopathologic findings of the labyrinthine segment of the facial nerve in a patient with test results indicating a poor prognosis (ie, with greater than 90 % degeneration by evoked EMG or complete lack of stimulation by maximal stimulation testing).
The histopathologic analysis of the facial nerve in our patient is limited to the labyrinthine segment. Since there was complete degeneration of the facial nerve at the time of exploration, we could not confirm the area at the meatal foramen as the location of the block by intraoperative evoked EMG. The presence of a sharply demarcated junction between identifiable nerve fibers and necrotic nerve at the meatal foramen of the fallopian canal is highly suggestive that this is the location of the nerve conductivity block. These findings are consistent with Fisch's designation of this area as a physiologic "bottleneck" and would support the logic of performing surgical decompression specifically directed at the labyrinthine segment via the middle fossa approach. Efficacy is yet to be established, but preliminary data are encouraging. 7 SUMMARY
The identification of a sharply defined demarcation between identifiable nerve fibers and necrotic nerve at the meatal foramen of the fallopian canal
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
Jackson et al, Labyrinthine Segment of Facial Nerve
in a patient with herpes zoster oticus is histopathologic confirmation of the concept of strangulation of the nerve fibers at this narrow junction in the
329
presence of edema, The rationale for a surgical decompression directed to the labyrinthine segment is supported,
REFERENCES 1. May M, Podvinec M, Ulrich J, Peiterson E, Klein S. Idiopathic (Bell's) palsy, herpes zoster cephalicus and other facial nerve disorders of viral origin. In: May M, ed. The facial nerve. New York: Thieme Inc, 1986:365-99. 2. Fisch U. Surgery for Bell's palsy. Arch Otolaryngol 1981; 107:1-11. 3. Fisch U, Esselen E. Total intratemporal exposure of the facial nerve. Arch Otolaryngol 1972;95:335-41. 4. Fisch U. Total facial nerve decompression and electroneuronography. In: Silverstein H, Norrell H, eds. Neurological sur-
gery of the ear. Birmingham, Ala: Aesculapius Publishing Co, 1977:21-33. 5. Robillard RB, Hilsinger RL, Adour KK. Ramsay Hunt facial paralysis: clinical analyses of 185 patients. Otolaryngol Head Neck Surg 1986;95:292-7. 6. Fowler EP. The pathologic findings in a case of facial paralysis. Trans Am Acad Ophthalmol OtolaryngoI1963;67: 187-97. 7. Gantz BJ. Idiopathic facial paralysis. In: Gates GA, ed. Current therapy in otolaryngology-head and neck surgery. 3rd ed. Philadelphia: BC Decker, 1987:62-6.
EDITOR'S COMMENTS This is a landmark paper and will be widely cited in the future. For the first time, pathologic evidence is established that the precise point of the lesion in a case of facial paralysis in a disease producing edema of the nerve is in the narrowest part of its bony tube, the meatal segment (as Fisch postulated). The great importance of this discovery is that it puts nearly the last brick into place in the long construction of the surgical decision as to where decompression should be carried out: not in the vertical course of the nerve, but in the meatal segment. Otology is enriched by this paper. Brian F. McCabe, MD Editor
XX INTERNATIONAL CONGRESS OF AUDIOLOGY The XX International Congress of Audiology will be held October 14-18, 1990, in Tenerife, Canary Islands, Spain. For further information, contact Dr Jose Barajas, Presidente, C/Perez de Rozas, 8, 38004 Santa Cruz de Tenerife, Canary Islands, Spain; telephone 22 27 54 88; telex 91106.
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
PATHOLOGIC FINDINGS IN THE LABYRINTHINE SEGMENT OF THE FACIAL NERVE IN A CASE OF FACIAL PARALYSIS C. GARY JACKSON, MD
GLENN D. JOHNSON,
NASHVILLE, TENNESSEE
VINCENT J. HYAMS, WASHINGTON,
MD
HANOVER, NEW HAMPSHIRE
MD
DENNIS
DC
S. POE, MD
BURLINGTON, MASSACHUSETTS
The histopathologic findings for a patient with acute facial paralysis caused by herpes zoster oticus who obtained no return of active facial function after 1 year are presented. All imaging studies were nondiagnostic. Biopsy of the labyrinthine segment was performed. Histopathologic analysis showed a sharp line of demarcation between sclerotic nerve proximal to and necrotic nerve distal to the meatal foramen area of the fallopian canal. This finding is consistent with observations that the lesion producing Bell's palsy and herpes zoster oticus usually is situated at the meatal foramen. KEY WORDS -
facial paralysis, herpes zoster oticus.
INTRODUCTION
pression is initiated at or confined to the labyrinthine segment by use of a middle fossa approach.
The major controversy today in the management of the patient with idiopathic acute peripheral facial palsy is whether patients with poor prognostic tests should undergo surgical decompression of the facial nerve. Since 85 % of patients with Bell's palsy will experience a satisfactory return of facial function with no treatment, I electrodiagnostic tests are used to identify those patients with extensive degeneration and a high probability for poor functional return. Fisch" has recommended decompression when degeneration reaches 90 % to 94 % by electroneurography within 3 weeks of onset of paralysis. Intraoperative evoked electromyography (EMG) has shown that the lesion producing Bell's palsy is located at the meatal foramen of the fallopian canal in 94 % of patients." Therefore, decom-
The location of the lesion in Bell's palsy at the meatal foramen (the entrance of the fallopian canal at the fundus of the internal auditory canal) is consistent with the known anatomy of this region. The loosely arranged intrameatal fibers of the facial nerve are constricted in the meatal foramen to form a fibrous ligament. 2 The meatal foramen is approximately 0.61 mm in diameter" and is the narrowest portion of the fallopian canal. Fisch" has referred to this area as a "physiologic bottleneck," in which the facial nerve fibers are literally strangulated in the presence of inflammatory edema. The facial paralysis associated with herpes zoster oticus has, in general, a worse prognosis than that
Labyrinthine section of facial nerve. A) Schematic of middle fossa exposure. Shaded area - biopsied segment of facial nerve. B) Facial nerve at point of constriction in meatal foramen of fallopian canal (H & E, original x400). Left side of photograph shows essentially normal nerve, with sharp demarcation from necrotic, fibrotic anuclear nerve fragment on right. From The Otology Group. Nashville, Tennessee (jackson, Johnson, Poe), and the Armed Forces Institute of Pathology, Washington, DC (Hyams). REPRINTS - C. Gary Jackson, MD, The Otology Group, 1811 State St, Nashville, TN 37203.
327
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
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Jackson et al, Labyrinthine Segment of Facial Nerve
caused by Bell's palsy.' Although the cause of the edema is different in these two conditions, the location of the nerve conductivity block, as measured by intraoperative evoked EMG, is the same, ie, the meatal foramen. 4 This localization has been explained by both anatomic and electrophysiologic studies, but there has been no histopathologic confirmation. A case of a patient with herpes zoster oticus that resulted in a poor return of function is presented. Biopsy of the labyrinthine segment of the facial nerve demonstrated a sharp demarcation between sclerotic and necrotic nerve at the meatal foramen. CASE REPORT
The patient is a 33-year-old woman who developed an acute, complete left facial palsy accompanied by ear pain, aural vesicles, and dizziness. She had no hearing loss. Her facial paralysis persisted without improvement for 6 months, when facial nerve stimulation testing elicited no response on the left at 6.5 rn A. The nerve appeared normal on transmastoid facial nerve decompression, but no return of function was observed after 6 months. She was referred to The Otology Group, PC, where 1 year after the onset of paralysis she exhibited a complete left facial paralysis. There was no response on the left to maximal stimulation electrical testing. Electromyography indicated total denervation of facial musculature with no signs of regeneration. Results of audiometry and auditory brain stem response testing were normal. Highresolution computed tomograms of the temporal bone and magnetic resonance images of the posterior fossa and intratemporal facial nerve were normal except for changes from the transmastoid decompression. The lack of facial nerve function after 1 year demanded exploration of the facial nerve despite nondiagnostic imaging studies. When the labyrinthine and internal auditory canal segments of the facial nerve were explored through a middle fossa approach, the intratympanic and internal auditory canal segments of the nerve appeared normal. However, the labyrinthine segment had the appearance of devitalized nerve. A biopsy sample of the labyrinthine segment was taken (see Figure, A), and there was no evidence of tumor on frozen section. A hypoglossal-facial nerve anastomosis then was performed. HISTOPATHOLOGY
The permanent hematoxylin and eosin-stained histologic sections from the facial nerve biopsy sample (labyrinthine section at the meatal foramen of the fallopian canal) showed a sharp demarcation of the proximal portion of the nerve, in which there was essentially normal histology except for a slight
sclerotic appearance. Schwann cells and perineural connective tissue were prominent in the normal nerve section and were differentiated from the distal nerve portion, in which there was a mixed fibrotic and necrotic anuclear micromorphology. There were scattered collections of small, round inflammatory cells within the distal necrotic nerve segment (see Figure, B). DISCUSSION
Most of the histopathologic findings reported with Bell's palsy and herpes zoster oticus are the result of postmortem studies. May et al' note that degeneration, hemorrhage, and inflammatory infiltrates are present in the facial nerves of patients who had idiopathic palsy and herpes zoster oticus, Fowler" described the findings for the facial nerve of a patient 14 days after onset of paralysis who had chronaxie studies indicating complete degeneration of all muscles supplied by the paralyzed facial nerve. There were fresh hemorrhages in the internal auditory canal between the region of Scarpa's ganglion and the narrow bony channel of the porus acousticus. Also noted in this region were neural sheaths that looked swollen and empty. It is difficult to interpret the significance of these researchers' findings, since there is great variability in the duration between onset of facial paralysis and death and in the severity of paralysis. There are very few reports in which degree of palsy and results of prognostic tests are available.' We are unaware of any reports of the histopathologic findings of the labyrinthine segment of the facial nerve in a patient with test results indicating a poor prognosis (ie, with greater than 90 % degeneration by evoked EMG or complete lack of stimulation by maximal stimulation testing).
The histopathologic analysis of the facial nerve in our patient is limited to the labyrinthine segment. Since there was complete degeneration of the facial nerve at the time of exploration, we could not confirm the area at the meatal foramen as the location of the block by intraoperative evoked EMG. The presence of a sharply demarcated junction between identifiable nerve fibers and necrotic nerve at the meatal foramen of the fallopian canal is highly suggestive that this is the location of the nerve conductivity block. These findings are consistent with Fisch's designation of this area as a physiologic "bottleneck" and would support the logic of performing surgical decompression specifically directed at the labyrinthine segment via the middle fossa approach. Efficacy is yet to be established, but preliminary data are encouraging. 7 SUMMARY
The identification of a sharply defined demarcation between identifiable nerve fibers and necrotic nerve at the meatal foramen of the fallopian canal
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
Jackson et al, Labyrinthine Segment of Facial Nerve
in a patient with herpes zoster oticus is histopathologic confirmation of the concept of strangulation of the nerve fibers at this narrow junction in the
329
presence of edema, The rationale for a surgical decompression directed to the labyrinthine segment is supported,
REFERENCES 1. May M, Podvinec M, Ulrich J, Peiterson E, Klein S. Idiopathic (Bell's) palsy, herpes zoster cephalicus and other facial nerve disorders of viral origin. In: May M, ed. The facial nerve. New York: Thieme Inc, 1986:365-99. 2. Fisch U. Surgery for Bell's palsy. Arch Otolaryngol 1981; 107:1-11. 3. Fisch U, Esselen E. Total intratemporal exposure of the facial nerve. Arch Otolaryngol 1972;95:335-41. 4. Fisch U. Total facial nerve decompression and electroneuronography. In: Silverstein H, Norrell H, eds. Neurological sur-
gery of the ear. Birmingham, Ala: Aesculapius Publishing Co, 1977:21-33. 5. Robillard RB, Hilsinger RL, Adour KK. Ramsay Hunt facial paralysis: clinical analyses of 185 patients. Otolaryngol Head Neck Surg 1986;95:292-7. 6. Fowler EP. The pathologic findings in a case of facial paralysis. Trans Am Acad Ophthalmol OtolaryngoI1963;67: 187-97. 7. Gantz BJ. Idiopathic facial paralysis. In: Gates GA, ed. Current therapy in otolaryngology-head and neck surgery. 3rd ed. Philadelphia: BC Decker, 1987:62-6.
EDITOR'S COMMENTS This is a landmark paper and will be widely cited in the future. For the first time, pathologic evidence is established that the precise point of the lesion in a case of facial paralysis in a disease producing edema of the nerve is in the narrowest part of its bony tube, the meatal segment (as Fisch postulated). The great importance of this discovery is that it puts nearly the last brick into place in the long construction of the surgical decision as to where decompression should be carried out: not in the vertical course of the nerve, but in the meatal segment. Otology is enriched by this paper. Brian F. McCabe, MD Editor
XX INTERNATIONAL CONGRESS OF AUDIOLOGY The XX International Congress of Audiology will be held October 14-18, 1990, in Tenerife, Canary Islands, Spain. For further information, contact Dr Jose Barajas, Presidente, C/Perez de Rozas, 8, 38004 Santa Cruz de Tenerife, Canary Islands, Spain; telephone 22 27 54 88; telex 91106.
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
