Clinical Oncology (1990) 2:138-141 © 1990 The Royal College of Radiologists
Clinical Oncology
Original Article Cranial Nerve Involvement by Nasopharyngeal Carcinoma: Response to Treatment and Clinical Significance S. F. Leung, S. Y. Tsao, P. Teo and W. Foo Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong
Abstract. The incidence of cranial nerve involvement in a group of 564 patients with nasopharyngeal carcinoma was 12%. Most of these patients had multiple cranial nerve involvement with the fifth and sixth nerves being most commonly affected. Different cranial nerves had different chances of recovery after radiotherapy. About half the patients with cranial nerve palsies had complete neurological recovery after radiotherapy. The cranial nerve response, however, was not a significant predictor of local tumour control.
anterior "t
.
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Keywords: Chemotherapy; Cranial nerves; Nasopharyngeal carcinoma; Radiotherapy ~wy 0dl,~lr)
INTRODUCTION
~mon
h ' ~ o g ~ CamaOal)
Nasopharyngeal carcinoma (NPC) is unique among head and neck cancers in its propensity to involve cranial nerves (CNs), partly owing to the proximity of the nasopharynx to the base of skull (Fig. 1). The cranial nerves may be involved along their intracranial course (e.g. CNs III-VI while coursing lateral to the sphenoid sinus, Fig. 2), at their passage through the bony skull base (Fig. 1), or below the skull base (e.g. CNs IX-XII at the parapharyngeal region). The incidence of cranial nerve deficits has been reported at 9% to 50% (Hoppe et al., 1976; Mesic et al., 1981; Ho, 1982; Petrovich et al., 1982; Stillwagon et al., 1986). However, there is little information in the literature
Correspondence and offprint requests to: Dr S. F. Leung, Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong.
F i g . 1. Diagram of a superomedial view of the right half of the
base of the skull. The r~lation of the nasopharynx to foramina of passage of cranial nerves is shown. Carvemot~
, ,._9
Fig. 2. Diagram of a coronal section through the spheroid sinus and roof of the nasopharynx. Relative positions of cranial nerves III-VI to the nasopharynx are shown. The arrow indicates the probable avenue of spread of the tumour.
139
Cranial Nerve Involvement by Nasopharyngeal Carcinoma
regarding the response of such cranial nerve deficits to radiotherapy. This report presents our experience with 59 patients. The relationship between neurological recovery and local tumour control is addressed.
function. CT of the nasopharynx and skull base were also performed for these situations.
RESULTS
PATIENTS AND METHOD
Of the 564 patients with newly diagnosed NPC presenting to the Prince of Wales Hospital, Hong Kong, from January 1985 to December 1987, 66 had cranial nerve involvement and formed the subject of this retrospective study. Five of these patients died before completion of radiotherapy. Another patient was treated with a palliative dose. One other patient did not receive radiotherapy because of presence of distant metastases. The remaining 59 patients were evaluable for response of neurological deficit to treatment. The first cranial nerve was not routinely examined. Dysfunction of the eighth nerve was not included in this report since the frequent occurrence of serous otitis media limited the certainty of diagnosis of involvement of this nerve in some cases. All patients had computed tomography (CT) evaluation of the nasopharynx and skull base as part of the staging procedure. All except one of the 59 evaluable patients received radical radiotherapy treatment to a dose equivalent to 60 Gy in 24 fractions over 6 weeks to the nasopharynx and bony structures at and below the skull base. Sixteen patients also received neoadjuvant chemotherapy treatment with a cisplatinum5FU scheme (Teo et al., 1989). The recovery of cranial nerves was determined at one month after completion of radiotherapy treatment. This timepoint was chosen as it corresponded to the first follow-up visit when the acute reactions from radiotherapy had largely subsided. The median followup time was 18 months. Complete recovery and absence of recovery were defined by clinical examination of cranial nerves. Partial recovery (with respect to individual patients) was defined as the presence of partial recovery of one or more of the involved cranial nerves (such as lessening in the degree of numbness or paraesthesia of CN V dermatomes or changes in corneal-canthal separation as a measurement of the degree of CN VI dysfunction) or complete recovery of one or more but not all of the involved nerves. The diagnosis of local tumour failure was based on either (1) persistence/recurrence of tumour at the nasopharynx. (2) persistence/recurrence of symptoms and signs suggestive of base-of-skull involvement, or (3) progression/re-appearance of cranial nerve dys-
Incidence The incidence of cranial nerve involvement at diagnosis was 12% (66/564). In the subgroup of 177 patients who had CT scan evidence of involvement of the base of skull, the incidence of cranial nerve involvement was 29% (52/177). Of 66 patients with cranial nerve involvement 21% (14/66) did not have CT evidence of erosion of the skull base.
Frequency of Individual Cranial Nerve Involvement Fig. 3 shows the relative frequencies of involvement of individual cranial nerves. CNs V and VI were those most commonly involved, whereas involvement of CNs II, III or VII was relatively rare. CNs III, IV, V and VI were frequently involved together, as were CNs IX, X, XI and XII. CNs III
100
= 9oE ~
80-
(44)
70-
(No. of patients with CN involvement)
Z 60x:
'~ m
50-
~-
30-
132)
(30) R~ '~"
~~]
"6 20-
(11}
10- 14) ~
o ~i Cranial nerve ~
II
(29) (16)
(13) (13)
[~ i
]
i
III
IV
V1
V2 V3 Vrn Vl VII IX X
XI XII Homer's I i
~
o . . . .
10/e) :
10_ N N N N
20 S
30 "~ ~ 40-
~ ~
t~21 (7/32) (3/11)-- (~0/44) (10/30)
(4/13)
'E 50-
),
(6/16)
r(4/9) 13/6) (CR/No.of patients in each group)
"6 60-
708090100
Fig. 3. (a) Relative frequencies of involvement and (b) ultimate complete recovery rates of individual cranial nerves. Total number of patients = 66 in (a) and 59 in (b).
140
S. F. Leung et al.
and VII were never involved alone, indicating that NPC is an unlikely diagnosis in such a scenario.
Symptomatology
Headache Of the 50 patients with involvement of one or more branches of the fifth nerve, 27 (54%) had a history of headache for a median duration of 3 months before the diagnosis of NPC. Ten patients (20%) had facial paraesthesia, 23 (40%) had facial numbness, whereas 11 (22%) had neither of these symptoms.
Diplopia Of the 31 patients with involvement of one or more of CN III, IV and VI, only 12 (39%) had diplopia on presentation, for a median duration of 2 months.
Impaired vision Of the three patients who had involvement of CN II, all had a history of impaired vision, the median duration being one month. There were six other patients with a history of impaired vision, they had involvement of one or more of CN III, IV and VI.
Recovery of Cranial Nerve Deficits After Radiotherapy and its Relation to Local Tumour Failure Fig. 4 shows the number of patients with complete, partial and no recovery of cranial nerve deficits at different points of time after radiotherapy. The 16
patients who had complete recovery at one month after radiotherapy included two patients who had complete recovery after neoadjuvant chemotherapy prior to radiotherapy. Referring to the recovery status at one month after radiotherapy, the 2-year local tumour failure rates of the complete, partial and non-responders were 12%, 31% and 55% respectively. Thus there was a 45% probability for patients who had no recovery of their cranial nerve deficits to be free from local recurrence at a median follow-up time of 18 months. Of the 29 patients with partial recovery, 10 achieved ultimate complete recovery at a follow-up time of 2 to 17 months. The ultimate response status did not correlate significantly with the 2-year local tumour failure rate in the partial responders. Fig. 5 shows that although there might be a trend towards less local failures for the responders, the difference did not reach statistical significance.
Recovery of Individual Cranial Nerves Fig. 3 also shows the ultimate complete recovery rates for individual cranial nerves. The third, the first branch of the fifth and the last four cranial nerves had a recovery rate of 50% or more, whereas the second, sixth, the seventh cranial nerves and the sympathetic nerve had a recovery rate below 10%. By dividing the cranial nerves into an anterior (CN II-VII) and a posterior (CN IX-XII) group, it can be seen that the three patients with involvement limited to the posterior group all had a complete recovery (Table 1). Patients with involvement of
100 I
!
90
,
I
80
I 1
70 atlmonth after RT
[
[atamedian ] follow up of 18 months
_
16 (27%) patients with COMPLETE RECOVERY 59 patients / with cranial / nerve(s) involvement ~
29 (49%) / patients with / = PARTIAL RECOVERY
10 patients COMPLETE RECOVERY
26 (44%) ~- patients with COMPLETE RECOVERY
60 5o 40
30All P v a l u e s > 0.15 20-
19 (32%) patients with =- PARTIAL RECOVERY
100 0
01.5
1
2i
1.5
215
Follow-up time (Years) k
10/24%) patients with NO RECOVERY
10 (24%) patients with '~ NO RECOVERY
Fig. 4. Recovery rates of cranial nerve deficits at one month after radiotherapy and at subsequent follow-up.
...... No r e c o v e r y (16 p a t i e n t s )
-- -- Partial r e c o v e r y (29 p a t i e n t s )
~
Complete recovery (14 p a t i e n t s )
Fig. 5. Actuarial local tumour failure rate according to response status of cranial nerves at one month after completion of radiotherapy.
141
Cranial Nerve Involvement by Nasopharyngeal Carcinoma
both the anterior and posterior groups had a very low complete recovery rate (29%). Table 1. Recovery rate according to anterior/posterior grouping of cranial nerves
Complete recovery (No. of patients) Anterior group 21 involvement only (CN I-VII) Posterior group 3 involvement only (CN IX-XII) Both 5
Incomplete recovery (No. of patients)
% Complete recovery
18
54
0
100
12
29
DISCUSSION
The 12% incidence of cranial nerve involvement in this report is on the low side of the range reported by others. An incidence as high as 50% was reported by Stillwagon et al. (1986) in their series of 36 patients. There is no apparent explanation of the discrepancy. The difference in the incidence of involvement of different cranial nerves and the difference in their recovery rates were remarkable. The proximity of some cranial nerves to the nasopharynx could explain their relatively frequent involvement. The first two branches of CN V and CN VI are located lower than CNs III and IV at the cavernous sinus (Fig. 2) and are thus likely to be involved earlier by cephalad extension of tumour through the foraman lacerum, with or withoutbony erosion of the sphenoid sinus. The different durations of involvement of the nerves roughly correlates with the likelihood of recovery. For example, CN III which is situated further away from the nasopharynx than CNs V and VI had a higher recovery rate than the latter nerves. Involvement of one or more of the last four cranial nerves was rarely associated with CT scan evidence of bony erosion at the jugular foramen or hypoglossal canal. Instead, the retrostyloid component of the para-
pharyngeal region was invariably infiltrated. The relatively favourable recovery rate of the last four nerves remains to be explained. Almost half the patients with cranial nerve involvement by NPC in this study had complete recovery of the neurological deficits after radiotherapy, although the recovery may take several months to complete. A further one-quarter had partial recovery. Although it is generally held that neural tissue is susceptible to permanent damage even after rectification of the inflicting cause, the high recovery rate in this study underlines the potential for functional recovery of the cranial nerves. However, the recovery of cranial nerve function is not a strong predictor of local tumour control. There is no statistically significant difference in the local failure rate between the responders and the non-responders, although there seems to be a tendency for the complete resonders to be at a lower risk. A larger patient population is required to define this issue more precisely and a longer follow-up time is required to assess the relation between cranial nerve recovery and eventual primary tumour control.
Acknowledgement. We would like to thank Mr Peter Yu, MSc for preparing the charts and tables and statistical calculations, and Ms Wendy Wong for secretarial assistance.
References Ho JHC (1982). Treatment of Cancer, pp. 251. Chapman and Hall, London. Hoppe RT, Goffinet DR, Bagshaw MA (1976). Carcinoma of the nasopharynx. Cancer, 37, 2605-2612. Mesic JB, Fletcher GH, Goepfert H (1981). Megavoltage irradiation of epithelial tumour of the nasopharynx. Inter-
national Journal of Radiation Oncology, Biology, Physics, 7, 447-453. Petrovich Z, Cox JD, Roswit B, Mackintosh R, Middleton R, Ohanian M e t al. (1982). Advanced carcinoma of the nasopharynx. Radiology, 144, 905-908. Stillwagon GB, Lee DJ, Moses H, Kashima H, Harris A, John M. (1986). Response of cranial nerve abnormalities in nasopharyngeal carcinoma to radiation therapy. Cancer, 57, 22722274. Teo P, Tsao SY, Shiu W, Leung WT, Tsang V, Yu Petal. (1989). A clinical study of 407 cases of nasopharyngeal carcinoma in Hong Kong. International Journal of Radiation Oncology, Biology, Physics, 17, 515-530.
Received for publication August 1989 Accepted January 1990
Clinical Oncology
Original Article Cranial Nerve Involvement by Nasopharyngeal Carcinoma: Response to Treatment and Clinical Significance S. F. Leung, S. Y. Tsao, P. Teo and W. Foo Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong
Abstract. The incidence of cranial nerve involvement in a group of 564 patients with nasopharyngeal carcinoma was 12%. Most of these patients had multiple cranial nerve involvement with the fifth and sixth nerves being most commonly affected. Different cranial nerves had different chances of recovery after radiotherapy. About half the patients with cranial nerve palsies had complete neurological recovery after radiotherapy. The cranial nerve response, however, was not a significant predictor of local tumour control.
anterior "t
.
o ~ c foramen (11)
n
rn 0/2) fe 0/3) ~nL
Keywords: Chemotherapy; Cranial nerves; Nasopharyngeal carcinoma; Radiotherapy ~wy 0dl,~lr)
INTRODUCTION
~mon
h ' ~ o g ~ CamaOal)
Nasopharyngeal carcinoma (NPC) is unique among head and neck cancers in its propensity to involve cranial nerves (CNs), partly owing to the proximity of the nasopharynx to the base of skull (Fig. 1). The cranial nerves may be involved along their intracranial course (e.g. CNs III-VI while coursing lateral to the sphenoid sinus, Fig. 2), at their passage through the bony skull base (Fig. 1), or below the skull base (e.g. CNs IX-XII at the parapharyngeal region). The incidence of cranial nerve deficits has been reported at 9% to 50% (Hoppe et al., 1976; Mesic et al., 1981; Ho, 1982; Petrovich et al., 1982; Stillwagon et al., 1986). However, there is little information in the literature
Correspondence and offprint requests to: Dr S. F. Leung, Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong.
F i g . 1. Diagram of a superomedial view of the right half of the
base of the skull. The r~lation of the nasopharynx to foramina of passage of cranial nerves is shown. Carvemot~
, ,._9
Fig. 2. Diagram of a coronal section through the spheroid sinus and roof of the nasopharynx. Relative positions of cranial nerves III-VI to the nasopharynx are shown. The arrow indicates the probable avenue of spread of the tumour.
139
Cranial Nerve Involvement by Nasopharyngeal Carcinoma
regarding the response of such cranial nerve deficits to radiotherapy. This report presents our experience with 59 patients. The relationship between neurological recovery and local tumour control is addressed.
function. CT of the nasopharynx and skull base were also performed for these situations.
RESULTS
PATIENTS AND METHOD
Of the 564 patients with newly diagnosed NPC presenting to the Prince of Wales Hospital, Hong Kong, from January 1985 to December 1987, 66 had cranial nerve involvement and formed the subject of this retrospective study. Five of these patients died before completion of radiotherapy. Another patient was treated with a palliative dose. One other patient did not receive radiotherapy because of presence of distant metastases. The remaining 59 patients were evaluable for response of neurological deficit to treatment. The first cranial nerve was not routinely examined. Dysfunction of the eighth nerve was not included in this report since the frequent occurrence of serous otitis media limited the certainty of diagnosis of involvement of this nerve in some cases. All patients had computed tomography (CT) evaluation of the nasopharynx and skull base as part of the staging procedure. All except one of the 59 evaluable patients received radical radiotherapy treatment to a dose equivalent to 60 Gy in 24 fractions over 6 weeks to the nasopharynx and bony structures at and below the skull base. Sixteen patients also received neoadjuvant chemotherapy treatment with a cisplatinum5FU scheme (Teo et al., 1989). The recovery of cranial nerves was determined at one month after completion of radiotherapy treatment. This timepoint was chosen as it corresponded to the first follow-up visit when the acute reactions from radiotherapy had largely subsided. The median followup time was 18 months. Complete recovery and absence of recovery were defined by clinical examination of cranial nerves. Partial recovery (with respect to individual patients) was defined as the presence of partial recovery of one or more of the involved cranial nerves (such as lessening in the degree of numbness or paraesthesia of CN V dermatomes or changes in corneal-canthal separation as a measurement of the degree of CN VI dysfunction) or complete recovery of one or more but not all of the involved nerves. The diagnosis of local tumour failure was based on either (1) persistence/recurrence of tumour at the nasopharynx. (2) persistence/recurrence of symptoms and signs suggestive of base-of-skull involvement, or (3) progression/re-appearance of cranial nerve dys-
Incidence The incidence of cranial nerve involvement at diagnosis was 12% (66/564). In the subgroup of 177 patients who had CT scan evidence of involvement of the base of skull, the incidence of cranial nerve involvement was 29% (52/177). Of 66 patients with cranial nerve involvement 21% (14/66) did not have CT evidence of erosion of the skull base.
Frequency of Individual Cranial Nerve Involvement Fig. 3 shows the relative frequencies of involvement of individual cranial nerves. CNs V and VI were those most commonly involved, whereas involvement of CNs II, III or VII was relatively rare. CNs III, IV, V and VI were frequently involved together, as were CNs IX, X, XI and XII. CNs III
100
= 9oE ~
80-
(44)
70-
(No. of patients with CN involvement)
Z 60x:
'~ m
50-
~-
30-
132)
(30) R~ '~"
~~]
"6 20-
(11}
10- 14) ~
o ~i Cranial nerve ~
II
(29) (16)
(13) (13)
[~ i
]
i
III
IV
V1
V2 V3 Vrn Vl VII IX X
XI XII Homer's I i
~
o . . . .
10/e) :
10_ N N N N
20 S
30 "~ ~ 40-
~ ~
t~21 (7/32) (3/11)-- (~0/44) (10/30)
(4/13)
'E 50-
),
(6/16)
r(4/9) 13/6) (CR/No.of patients in each group)
"6 60-
708090100
Fig. 3. (a) Relative frequencies of involvement and (b) ultimate complete recovery rates of individual cranial nerves. Total number of patients = 66 in (a) and 59 in (b).
140
S. F. Leung et al.
and VII were never involved alone, indicating that NPC is an unlikely diagnosis in such a scenario.
Symptomatology
Headache Of the 50 patients with involvement of one or more branches of the fifth nerve, 27 (54%) had a history of headache for a median duration of 3 months before the diagnosis of NPC. Ten patients (20%) had facial paraesthesia, 23 (40%) had facial numbness, whereas 11 (22%) had neither of these symptoms.
Diplopia Of the 31 patients with involvement of one or more of CN III, IV and VI, only 12 (39%) had diplopia on presentation, for a median duration of 2 months.
Impaired vision Of the three patients who had involvement of CN II, all had a history of impaired vision, the median duration being one month. There were six other patients with a history of impaired vision, they had involvement of one or more of CN III, IV and VI.
Recovery of Cranial Nerve Deficits After Radiotherapy and its Relation to Local Tumour Failure Fig. 4 shows the number of patients with complete, partial and no recovery of cranial nerve deficits at different points of time after radiotherapy. The 16
patients who had complete recovery at one month after radiotherapy included two patients who had complete recovery after neoadjuvant chemotherapy prior to radiotherapy. Referring to the recovery status at one month after radiotherapy, the 2-year local tumour failure rates of the complete, partial and non-responders were 12%, 31% and 55% respectively. Thus there was a 45% probability for patients who had no recovery of their cranial nerve deficits to be free from local recurrence at a median follow-up time of 18 months. Of the 29 patients with partial recovery, 10 achieved ultimate complete recovery at a follow-up time of 2 to 17 months. The ultimate response status did not correlate significantly with the 2-year local tumour failure rate in the partial responders. Fig. 5 shows that although there might be a trend towards less local failures for the responders, the difference did not reach statistical significance.
Recovery of Individual Cranial Nerves Fig. 3 also shows the ultimate complete recovery rates for individual cranial nerves. The third, the first branch of the fifth and the last four cranial nerves had a recovery rate of 50% or more, whereas the second, sixth, the seventh cranial nerves and the sympathetic nerve had a recovery rate below 10%. By dividing the cranial nerves into an anterior (CN II-VII) and a posterior (CN IX-XII) group, it can be seen that the three patients with involvement limited to the posterior group all had a complete recovery (Table 1). Patients with involvement of
100 I
!
90
,
I
80
I 1
70 atlmonth after RT
[
[atamedian ] follow up of 18 months
_
16 (27%) patients with COMPLETE RECOVERY 59 patients / with cranial / nerve(s) involvement ~
29 (49%) / patients with / = PARTIAL RECOVERY
10 patients COMPLETE RECOVERY
26 (44%) ~- patients with COMPLETE RECOVERY
60 5o 40
30All P v a l u e s > 0.15 20-
19 (32%) patients with =- PARTIAL RECOVERY
100 0
01.5
1
2i
1.5
215
Follow-up time (Years) k
10/24%) patients with NO RECOVERY
10 (24%) patients with '~ NO RECOVERY
Fig. 4. Recovery rates of cranial nerve deficits at one month after radiotherapy and at subsequent follow-up.
...... No r e c o v e r y (16 p a t i e n t s )
-- -- Partial r e c o v e r y (29 p a t i e n t s )
~
Complete recovery (14 p a t i e n t s )
Fig. 5. Actuarial local tumour failure rate according to response status of cranial nerves at one month after completion of radiotherapy.
141
Cranial Nerve Involvement by Nasopharyngeal Carcinoma
both the anterior and posterior groups had a very low complete recovery rate (29%). Table 1. Recovery rate according to anterior/posterior grouping of cranial nerves
Complete recovery (No. of patients) Anterior group 21 involvement only (CN I-VII) Posterior group 3 involvement only (CN IX-XII) Both 5
Incomplete recovery (No. of patients)
% Complete recovery
18
54
0
100
12
29
DISCUSSION
The 12% incidence of cranial nerve involvement in this report is on the low side of the range reported by others. An incidence as high as 50% was reported by Stillwagon et al. (1986) in their series of 36 patients. There is no apparent explanation of the discrepancy. The difference in the incidence of involvement of different cranial nerves and the difference in their recovery rates were remarkable. The proximity of some cranial nerves to the nasopharynx could explain their relatively frequent involvement. The first two branches of CN V and CN VI are located lower than CNs III and IV at the cavernous sinus (Fig. 2) and are thus likely to be involved earlier by cephalad extension of tumour through the foraman lacerum, with or withoutbony erosion of the sphenoid sinus. The different durations of involvement of the nerves roughly correlates with the likelihood of recovery. For example, CN III which is situated further away from the nasopharynx than CNs V and VI had a higher recovery rate than the latter nerves. Involvement of one or more of the last four cranial nerves was rarely associated with CT scan evidence of bony erosion at the jugular foramen or hypoglossal canal. Instead, the retrostyloid component of the para-
pharyngeal region was invariably infiltrated. The relatively favourable recovery rate of the last four nerves remains to be explained. Almost half the patients with cranial nerve involvement by NPC in this study had complete recovery of the neurological deficits after radiotherapy, although the recovery may take several months to complete. A further one-quarter had partial recovery. Although it is generally held that neural tissue is susceptible to permanent damage even after rectification of the inflicting cause, the high recovery rate in this study underlines the potential for functional recovery of the cranial nerves. However, the recovery of cranial nerve function is not a strong predictor of local tumour control. There is no statistically significant difference in the local failure rate between the responders and the non-responders, although there seems to be a tendency for the complete resonders to be at a lower risk. A larger patient population is required to define this issue more precisely and a longer follow-up time is required to assess the relation between cranial nerve recovery and eventual primary tumour control.
Acknowledgement. We would like to thank Mr Peter Yu, MSc for preparing the charts and tables and statistical calculations, and Ms Wendy Wong for secretarial assistance.
References Ho JHC (1982). Treatment of Cancer, pp. 251. Chapman and Hall, London. Hoppe RT, Goffinet DR, Bagshaw MA (1976). Carcinoma of the nasopharynx. Cancer, 37, 2605-2612. Mesic JB, Fletcher GH, Goepfert H (1981). Megavoltage irradiation of epithelial tumour of the nasopharynx. Inter-
national Journal of Radiation Oncology, Biology, Physics, 7, 447-453. Petrovich Z, Cox JD, Roswit B, Mackintosh R, Middleton R, Ohanian M e t al. (1982). Advanced carcinoma of the nasopharynx. Radiology, 144, 905-908. Stillwagon GB, Lee DJ, Moses H, Kashima H, Harris A, John M. (1986). Response of cranial nerve abnormalities in nasopharyngeal carcinoma to radiation therapy. Cancer, 57, 22722274. Teo P, Tsao SY, Shiu W, Leung WT, Tsang V, Yu Petal. (1989). A clinical study of 407 cases of nasopharyngeal carcinoma in Hong Kong. International Journal of Radiation Oncology, Biology, Physics, 17, 515-530.
Received for publication August 1989 Accepted January 1990
