ORL 38: 3 4 4 -3 4 9 (1976)
Solitary Schwannoma of the Cervical Vagus Nerve Iain (V.5. Mair, Gudmund O. Marhaug and Helge Stalsberg Departments of Otolaryngology and Pathology, University of Tromsd, Tromsd
Key Words. Vagus schwannoma • Neurologic deficit • Cancer Abstract. A case of benign, solitary schwannoma of the cervical vagus nerve with ipsilateral vocal cord paralysis is presented. The differential diagnostic aspects are discussed, with special reference to neurologic deficit in association with this lesion. The possible occurrence of concomitant unrelated malignancy is emphasised.
The differential diagnosis of a lump in the neck is a problem frequently encountered in otolaryngological practice. In the adult, the presence of a persis tent mass in the lateral neck must be viewed with concern, since it has been estimated that approximately 7 0 -8 0 % of such swellings are malignant {Martin and Romieu, 1952), whilst coincident symptoms or signs of involvement of neighbouring structures are generally regarded as indicating an even poorer prognosis. The following case presents an exception to these generalisations, while at the same time illustrating an aspect of symptomatology on which there is con siderable disagreement in the literature.
Case Report
Received: May 7, 1976; accepted: July 6, 1976.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
A 71-year-old white male consulted his family doctor on account of a 5-month history of gradually increasing hoarseness. On referral to the Department of Otolaryngology, a right vocal cord paralysis and a tumour in the right, upper lateral neck were found, and the patient was admitted for further investigation.
Mair/Marhaug/Stalsberg
345
The previous medical history was unremarkable, apart form a severe bout of influenza in the week preceding admission to hospital. The sole complaint was of increasing weakness of the voice, the swelling in the neck being an incidental finding first discovered at the time of out-patient consultation. All laboratory investigations were non-contributory, apart from a raised SR and influenza A antibody titre, which were considered a sequel to the preceding influenza-like illness.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Fig. 1. a The tumour with attached stump of the vagus nerve emerging from the distal pole, b Cut surface of the tumour. Fig. 2. Typical schwannoma with Antoni type A structure. HE. X 350.
Mair/Marhaug/Stalsberg
346
General physical examination was negative. Indirect laryngoscopy revealed an im mobile right vocal cord in the paramedian position. Immediately postero-inferior to the angle of the right mandible, a smooth, firm, non-tender, 4 X 3 cm mass was palpated deep to the anterior border of the sternomastoid muscle. The tumour was mobile in all directions, and palpation did not elicit any reflex changes. The presumptive diagnosis was a metastatic mass in the neck with secondary infiltration of the vagus nerve, but an exhaustive clinical examination revealed no further abnormalities. Radiological investigations of thorax, skull, skull base and paranasal sinuses were non contributory, and gastro-intestinal tract studies were likewise negative. No changes sugges tive of primary tumour were found on endoscopic examination of the upper respiratory and gastro-intestinal tracts, and frozen section reports of deep nasopharyngeal biopsies revealed only normal mucosa and submucosa. Under the same general anaesthesia, a skin crease neck incision was, therefore, made, and the tumour exposed. Following incision of the deep cervical fascia, the internal jugular vein was found spread over the superficial aspect of the tumour, while the carotid vessels were displaced medially. The tumour was situated in the course of the vagus nerve, immediately distal to the point of origin of the superior laryngeal branch, and numerous, extremely thin nerve strands were visible splayed out over both poles and disappearing into the capsule. A frozen section showed benign schwannoma. In view of the pre-operative evidence of recurrent laryngeal nerve paralysis, it was decided to section the vagus nerve proximal and distal to the tumour while preserving the superior laryngeal branch intact. This was duly performed without any changes occurring in the continuously monitored ECG. The specimen (fig. 1 a) measured 35 X 30 X 25 mm with an attached 10-mm stump of the vagus nerve. The cut surface (fig. 1 b) was grayish white, with scattered haemorrhages, and the paraffin sections confirmed the diagnosis of benign schwannoma with predominance of Antoni type A tissue (fig. 2). The immediate post-operative course was uneventful, but approximately I year later the patient was admitted to the Department of Surgery and operated for an adenocarcinoma of the pyloric antrum, which subsequently resulted in his demise, 16 months after removal of the neck tumour.
There are three aspects of this case which are of interest and justify com ment on the literature. Firstly, the place of neurogenic tumours in the differen tial diagnosis of a lump in the neck, secondly the contentious question of the occurrence of neurological symptoms and signs in benign, extracranial schwan nomas, and lastly the possible association with malignancy in other regions of the body. There is considerable terminological confusion in the literature, and particu larly in the earlier reports, a wide variety of terms has been applied to the same pathological entity. The first adequate histological description of this tumour was by Verocay (1910), who designated it ‘neurinoma’. In 1935, Stout made the distinction between the neurilemmoma, which is a solitary, encapsulated tumour
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Discussion
347
of peripheral nerves and nerve roots, and the non-encapsulated neurofibroma typical of von Recklinghausen’s disease. Although ultrastructural studies have revealed the Schwann cell as the main component of both lesions, they are histologically and clinically distinct, and the preferred term schwannoma is used synonymously with neurilemmoma (Waggener, 1966; Russell and Rubinstein, 1971). The schwannoma which occurs in association with nerves outside the cranium and spinal cord is a solitary, well-encapsulated tumour, and the nerve fibres are either displaced to one side, or else splayed out over the surface, but do not penetrate into the substance of the tumour (Stout, 1935; Horwich and Hawe, 1962). Two different types of tissue are recognised (Antoni, 1920), both of which are characteristic for schwannomas. Cystic degeneration is a frequent feature (Stout, 1935), which may lead to diagnostic confusion with branchial cysts (Reddick and Myers, 1973). Most authors consider that malignant transfor mation is very unlikely in solitary schwannomas (Stout, 1935; DasGupta e ta l, 1969). The solitary extracranial schwannoma is a comparatively rare tumour with a surprising predilection for the head and neck. Approximately 44 % of two large series reported in the literature have occurred in the region of interest for oto laryngologists (Ehrlich and Martin, 1943; DasGupta et al, 1969). Frequently, however, the nerve of origin cannot be identified at operation, and this may partially account for the comparatively small number of vagal schwannomas reported in the literature. In consequence of the tumour’s comparative rarity, a correct pre-operative diagnosis is seldom made (Horwich and Hawe, 1962 \ Reddick and Myers, 1973). Slaughter and dePeyster( 1949) described a diagnostic syndrome in which impor tance was attached to medial displacement of the internal carotid artery by the tumour, but posterior positioning of this vessel has also been reported (Violé, 1946), and a recent angiographic study has confirmed that no diagnostic impor tance can be placed on the course of the major arteries relative to the neck mass (Skucas et al, 1973). Another diagnostic feature which has not survived the passage of time is the eliciting of a spasmodic cough following light palpation of the tumour (Leichtling et al, 1963). This sign was not present in our patient, nor was tumour mobility restricted to the horizontal plane (Horwich and Hawe, 1962). The clinical features of the neck swelling would, therefore, appear to be of little value in awakening suspicion of a vagal schwannoma. Unfortunately, the association of neurological signs, in this instance paralysis of the vocal cord, must also be regarded as having dubious diagnostic value. The overwhelming majority of reports of vagal schwannoma in the neck stress the absence of signs of interference with nerve function (DasGupta e ta l, 1969; Reddick and Myers, 1973). This feature is not confined to the cervical course of the vagus nerve, but
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Solitary Schwannoma o f the Cervical Vagus Nerve
Mair/Marhaug /Stalsberg
348
is apparently characteristic for solitary schwannomas of all peripheral nerves. DasGupta et al. (1969) in a study of 303 tumours of this type, stress the ‘remarkable absence of associated neurologic deficit’, and found no evidence of sensory or motor paralysis of the affected nerve trunk in any of their patients. A review of the literature has produced a total of 59 schwannomas of the vagus nerve in the neck in which the relevant clinical features are adequately documented. A pre-operative vocal cord paralysis was reported in only six patients. In the earliest of these cases (Bruckschwaiger, 1947), a second tumour was found in the brachial plexus, and café au lait spots were present in the skin, thus confirming the diagnosis of von Recklinghausen’s disease. Slaughter and dePeyster ( 1949) mention that their third case had a flaccid paralysis of the right vocal cord, but the tumour was very large and extended deeply into the hypopharynx producing laryngeal deformity and stridor. There was apparently no complaint of hoarseness, and indirect laryngoscopy in the immediate post operative period revealed normal cord function! In case No. 4 of Slaughter and dePeyster (1949) the ipsilateral vocal cord was paretic, but the neck tumour had been previously incised and drained on two occasions which may well have been contributory factors in the production of the cord paresis. There are unfortunately few details in the publication of Lindén and Hamberger (1954), but the cases of Cinca et al. (1973) and André et al. (1975) are adequately documented. We, therefore, consider the latter three reports, together with our own case, as the sole instances in which a solitary schwannoma of the cervical vagus nerve has been associated with pre-operative vocal cord paralysis. The evidence would, therefore, not support the view that dysphagia, vocal cord paralysis and medial displacement of the carotid artery are diagnostic for this tumour {Slaughter and dePeyster, 1949). DasGupta et al. (1969), in their previously mentioned study of 303 patients with solitary, extracranial schwannoma, reported that 49, or 16%, had an un related malignant tumour. Of these, seven cases were first discovered in the routine work-up of patients presenting for treatment of their schwannomas. We are in complete agreement with these authors that a careful study of this pos sible association is necessary, and that all patients with solitary schwannoma should be subjected to a thorough examination.
In der vorliegenden Arbeit wird über den Fall eines benignen, solitären Schwannoms berichtet, ausgehend von der zervikalen Portion des Nervus vagus. Es werden die differential diagnostischen Aspekte dieser Geschwulst besprochen, besonders im Hinblick auf die neuro logischen Ausfälle (homolaterale Stimmbandlähmung), welche durch diese Tumorform verursacht werden können.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Zusammenfassung
Solitary Schwannoma of the Cervical Vagus Nerve
349
Résumé Le cas d’un schwannome solitaire bénin issu de la portion cervicale du nerf vague est présenté dans ce travail. Le diagnostic différentiel de cette tumeur est ensuite discuté, en mettant l’accent sur les troubles neurologiques (paralysie laryngée homolatérale) qui peuvent être causés par ce genre de tumeur.
References
Iain (V.5. Mair, Department of Otolaryngology, University of Tromsÿ, 9000 Tromsfi, (Norway)
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
André, P.: l.accourreye, H. et Haguet, J.-F.: Tumeurs nerveuses parapharyngées. Ann. Oto laryngol. Chir. Cervicofac. 92: 345-356 (1975). Antoni, N.R.E.: Uber Rückenmarkstumoren und Neurofibrome (Bergmann, München 1920). Bruckschwaiger, O.: Ein Lall von Stammneurofibrom des Nervus vagus und die Bedeutung der Vagusreizsymptomc für die Klinik. Wien. med. Wschr. 97: 111-113 (1947). Cinca, D.; Suciu, M.; Sbenghe Têtu, L. et Mincu, D.: Considérations sur un cas de schwan nome latéro-cervical. Ann. Otolaryngol. Chir. Cervicofac. 90: 307-310 (1973). DasGupta, T.K.; Brasfield, R.D.; Strong, F.W., and Hajdu, S.I.: Benign solitary schwan nomas (neurilemmomas). Cancer 24: 355-366 (1969). Ehrlich, H.E. and Martin, H.: Schwannomas (neurilemmomas) in the head and neck. Surgery Gynec. Obstet. 76: 577-583 (1943). Horwich, M. and Hawe, P.: Neurilemmoma of the vagus nerve in the neck. Br. J. Surg.49: 443-446 (1962). Beichtling, J.L.; Lesnick, G.J., and Garlock, J.H.: Neurilemmomas of vagus nerve in the neck. J. Am. med. Ass. 183: 143-145 (1963). Linden, A. und Hornberger, C.-A.: Halsneurinom. Acta oto-lar. 116: suppl., pp. 205-211 (1954). Martin, H. and Romieu, C.: The diagnostic significance of a lump in the neck. Postgrad. Med. 11: 491-500 0952). Reddick, L.P. and Myers, R.T.: Neurilemmoma of the cervical portion of the vagus nerve. Am. J. Surg. 125: 744-747 (1973). Russell, D.S. and Rubinstein, L.J.: Pathology of tumours of the nervous system (Arnold, London 1971). Skucas, J.; Rossi, P.: Brinker, R.A., and Eberle, R.C.: Angiographic differentiation of neuro genic tumors at the carotid artery bifurcation. Surgery Gynec. Obstet. 137: 35-39 (1973). Slaughter, D.P. and dePeyster. F.A.: Pharyngeal neurilemmomas of cranial nerve origin. Archs Surg. 59: 386-397 (1949). Stout, A.P.: The peripheral manifestations of the specific nerve sheath tumor (neuri lemoma). Am. J. Cancer 24: 751-796 (1935). Verocay, J.: Zur Kenntnis der Neurofibrome. Beitr. Pathol. 48: 1-69 (1910). Violé, P.: Schwannoma of the pharynx. Ann. Otol. Rhinol. Lar. 55.' 334-341 (1946). Waggener, J.D.: Ultrastructure of benign peripheral nerve sheath tumors. Cancer 19: 6 9 9 709 (1966).
Solitary Schwannoma of the Cervical Vagus Nerve Iain (V.5. Mair, Gudmund O. Marhaug and Helge Stalsberg Departments of Otolaryngology and Pathology, University of Tromsd, Tromsd
Key Words. Vagus schwannoma • Neurologic deficit • Cancer Abstract. A case of benign, solitary schwannoma of the cervical vagus nerve with ipsilateral vocal cord paralysis is presented. The differential diagnostic aspects are discussed, with special reference to neurologic deficit in association with this lesion. The possible occurrence of concomitant unrelated malignancy is emphasised.
The differential diagnosis of a lump in the neck is a problem frequently encountered in otolaryngological practice. In the adult, the presence of a persis tent mass in the lateral neck must be viewed with concern, since it has been estimated that approximately 7 0 -8 0 % of such swellings are malignant {Martin and Romieu, 1952), whilst coincident symptoms or signs of involvement of neighbouring structures are generally regarded as indicating an even poorer prognosis. The following case presents an exception to these generalisations, while at the same time illustrating an aspect of symptomatology on which there is con siderable disagreement in the literature.
Case Report
Received: May 7, 1976; accepted: July 6, 1976.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
A 71-year-old white male consulted his family doctor on account of a 5-month history of gradually increasing hoarseness. On referral to the Department of Otolaryngology, a right vocal cord paralysis and a tumour in the right, upper lateral neck were found, and the patient was admitted for further investigation.
Mair/Marhaug/Stalsberg
345
The previous medical history was unremarkable, apart form a severe bout of influenza in the week preceding admission to hospital. The sole complaint was of increasing weakness of the voice, the swelling in the neck being an incidental finding first discovered at the time of out-patient consultation. All laboratory investigations were non-contributory, apart from a raised SR and influenza A antibody titre, which were considered a sequel to the preceding influenza-like illness.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Fig. 1. a The tumour with attached stump of the vagus nerve emerging from the distal pole, b Cut surface of the tumour. Fig. 2. Typical schwannoma with Antoni type A structure. HE. X 350.
Mair/Marhaug/Stalsberg
346
General physical examination was negative. Indirect laryngoscopy revealed an im mobile right vocal cord in the paramedian position. Immediately postero-inferior to the angle of the right mandible, a smooth, firm, non-tender, 4 X 3 cm mass was palpated deep to the anterior border of the sternomastoid muscle. The tumour was mobile in all directions, and palpation did not elicit any reflex changes. The presumptive diagnosis was a metastatic mass in the neck with secondary infiltration of the vagus nerve, but an exhaustive clinical examination revealed no further abnormalities. Radiological investigations of thorax, skull, skull base and paranasal sinuses were non contributory, and gastro-intestinal tract studies were likewise negative. No changes sugges tive of primary tumour were found on endoscopic examination of the upper respiratory and gastro-intestinal tracts, and frozen section reports of deep nasopharyngeal biopsies revealed only normal mucosa and submucosa. Under the same general anaesthesia, a skin crease neck incision was, therefore, made, and the tumour exposed. Following incision of the deep cervical fascia, the internal jugular vein was found spread over the superficial aspect of the tumour, while the carotid vessels were displaced medially. The tumour was situated in the course of the vagus nerve, immediately distal to the point of origin of the superior laryngeal branch, and numerous, extremely thin nerve strands were visible splayed out over both poles and disappearing into the capsule. A frozen section showed benign schwannoma. In view of the pre-operative evidence of recurrent laryngeal nerve paralysis, it was decided to section the vagus nerve proximal and distal to the tumour while preserving the superior laryngeal branch intact. This was duly performed without any changes occurring in the continuously monitored ECG. The specimen (fig. 1 a) measured 35 X 30 X 25 mm with an attached 10-mm stump of the vagus nerve. The cut surface (fig. 1 b) was grayish white, with scattered haemorrhages, and the paraffin sections confirmed the diagnosis of benign schwannoma with predominance of Antoni type A tissue (fig. 2). The immediate post-operative course was uneventful, but approximately I year later the patient was admitted to the Department of Surgery and operated for an adenocarcinoma of the pyloric antrum, which subsequently resulted in his demise, 16 months after removal of the neck tumour.
There are three aspects of this case which are of interest and justify com ment on the literature. Firstly, the place of neurogenic tumours in the differen tial diagnosis of a lump in the neck, secondly the contentious question of the occurrence of neurological symptoms and signs in benign, extracranial schwan nomas, and lastly the possible association with malignancy in other regions of the body. There is considerable terminological confusion in the literature, and particu larly in the earlier reports, a wide variety of terms has been applied to the same pathological entity. The first adequate histological description of this tumour was by Verocay (1910), who designated it ‘neurinoma’. In 1935, Stout made the distinction between the neurilemmoma, which is a solitary, encapsulated tumour
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Discussion
347
of peripheral nerves and nerve roots, and the non-encapsulated neurofibroma typical of von Recklinghausen’s disease. Although ultrastructural studies have revealed the Schwann cell as the main component of both lesions, they are histologically and clinically distinct, and the preferred term schwannoma is used synonymously with neurilemmoma (Waggener, 1966; Russell and Rubinstein, 1971). The schwannoma which occurs in association with nerves outside the cranium and spinal cord is a solitary, well-encapsulated tumour, and the nerve fibres are either displaced to one side, or else splayed out over the surface, but do not penetrate into the substance of the tumour (Stout, 1935; Horwich and Hawe, 1962). Two different types of tissue are recognised (Antoni, 1920), both of which are characteristic for schwannomas. Cystic degeneration is a frequent feature (Stout, 1935), which may lead to diagnostic confusion with branchial cysts (Reddick and Myers, 1973). Most authors consider that malignant transfor mation is very unlikely in solitary schwannomas (Stout, 1935; DasGupta e ta l, 1969). The solitary extracranial schwannoma is a comparatively rare tumour with a surprising predilection for the head and neck. Approximately 44 % of two large series reported in the literature have occurred in the region of interest for oto laryngologists (Ehrlich and Martin, 1943; DasGupta et al, 1969). Frequently, however, the nerve of origin cannot be identified at operation, and this may partially account for the comparatively small number of vagal schwannomas reported in the literature. In consequence of the tumour’s comparative rarity, a correct pre-operative diagnosis is seldom made (Horwich and Hawe, 1962 \ Reddick and Myers, 1973). Slaughter and dePeyster( 1949) described a diagnostic syndrome in which impor tance was attached to medial displacement of the internal carotid artery by the tumour, but posterior positioning of this vessel has also been reported (Violé, 1946), and a recent angiographic study has confirmed that no diagnostic impor tance can be placed on the course of the major arteries relative to the neck mass (Skucas et al, 1973). Another diagnostic feature which has not survived the passage of time is the eliciting of a spasmodic cough following light palpation of the tumour (Leichtling et al, 1963). This sign was not present in our patient, nor was tumour mobility restricted to the horizontal plane (Horwich and Hawe, 1962). The clinical features of the neck swelling would, therefore, appear to be of little value in awakening suspicion of a vagal schwannoma. Unfortunately, the association of neurological signs, in this instance paralysis of the vocal cord, must also be regarded as having dubious diagnostic value. The overwhelming majority of reports of vagal schwannoma in the neck stress the absence of signs of interference with nerve function (DasGupta e ta l, 1969; Reddick and Myers, 1973). This feature is not confined to the cervical course of the vagus nerve, but
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Solitary Schwannoma o f the Cervical Vagus Nerve
Mair/Marhaug /Stalsberg
348
is apparently characteristic for solitary schwannomas of all peripheral nerves. DasGupta et al. (1969) in a study of 303 tumours of this type, stress the ‘remarkable absence of associated neurologic deficit’, and found no evidence of sensory or motor paralysis of the affected nerve trunk in any of their patients. A review of the literature has produced a total of 59 schwannomas of the vagus nerve in the neck in which the relevant clinical features are adequately documented. A pre-operative vocal cord paralysis was reported in only six patients. In the earliest of these cases (Bruckschwaiger, 1947), a second tumour was found in the brachial plexus, and café au lait spots were present in the skin, thus confirming the diagnosis of von Recklinghausen’s disease. Slaughter and dePeyster ( 1949) mention that their third case had a flaccid paralysis of the right vocal cord, but the tumour was very large and extended deeply into the hypopharynx producing laryngeal deformity and stridor. There was apparently no complaint of hoarseness, and indirect laryngoscopy in the immediate post operative period revealed normal cord function! In case No. 4 of Slaughter and dePeyster (1949) the ipsilateral vocal cord was paretic, but the neck tumour had been previously incised and drained on two occasions which may well have been contributory factors in the production of the cord paresis. There are unfortunately few details in the publication of Lindén and Hamberger (1954), but the cases of Cinca et al. (1973) and André et al. (1975) are adequately documented. We, therefore, consider the latter three reports, together with our own case, as the sole instances in which a solitary schwannoma of the cervical vagus nerve has been associated with pre-operative vocal cord paralysis. The evidence would, therefore, not support the view that dysphagia, vocal cord paralysis and medial displacement of the carotid artery are diagnostic for this tumour {Slaughter and dePeyster, 1949). DasGupta et al. (1969), in their previously mentioned study of 303 patients with solitary, extracranial schwannoma, reported that 49, or 16%, had an un related malignant tumour. Of these, seven cases were first discovered in the routine work-up of patients presenting for treatment of their schwannomas. We are in complete agreement with these authors that a careful study of this pos sible association is necessary, and that all patients with solitary schwannoma should be subjected to a thorough examination.
In der vorliegenden Arbeit wird über den Fall eines benignen, solitären Schwannoms berichtet, ausgehend von der zervikalen Portion des Nervus vagus. Es werden die differential diagnostischen Aspekte dieser Geschwulst besprochen, besonders im Hinblick auf die neuro logischen Ausfälle (homolaterale Stimmbandlähmung), welche durch diese Tumorform verursacht werden können.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
Zusammenfassung
Solitary Schwannoma of the Cervical Vagus Nerve
349
Résumé Le cas d’un schwannome solitaire bénin issu de la portion cervicale du nerf vague est présenté dans ce travail. Le diagnostic différentiel de cette tumeur est ensuite discuté, en mettant l’accent sur les troubles neurologiques (paralysie laryngée homolatérale) qui peuvent être causés par ce genre de tumeur.
References
Iain (V.5. Mair, Department of Otolaryngology, University of Tromsÿ, 9000 Tromsfi, (Norway)
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 2:33:01 PM
André, P.: l.accourreye, H. et Haguet, J.-F.: Tumeurs nerveuses parapharyngées. Ann. Oto laryngol. Chir. Cervicofac. 92: 345-356 (1975). Antoni, N.R.E.: Uber Rückenmarkstumoren und Neurofibrome (Bergmann, München 1920). Bruckschwaiger, O.: Ein Lall von Stammneurofibrom des Nervus vagus und die Bedeutung der Vagusreizsymptomc für die Klinik. Wien. med. Wschr. 97: 111-113 (1947). Cinca, D.; Suciu, M.; Sbenghe Têtu, L. et Mincu, D.: Considérations sur un cas de schwan nome latéro-cervical. Ann. Otolaryngol. Chir. Cervicofac. 90: 307-310 (1973). DasGupta, T.K.; Brasfield, R.D.; Strong, F.W., and Hajdu, S.I.: Benign solitary schwan nomas (neurilemmomas). Cancer 24: 355-366 (1969). Ehrlich, H.E. and Martin, H.: Schwannomas (neurilemmomas) in the head and neck. Surgery Gynec. Obstet. 76: 577-583 (1943). Horwich, M. and Hawe, P.: Neurilemmoma of the vagus nerve in the neck. Br. J. Surg.49: 443-446 (1962). Beichtling, J.L.; Lesnick, G.J., and Garlock, J.H.: Neurilemmomas of vagus nerve in the neck. J. Am. med. Ass. 183: 143-145 (1963). Linden, A. und Hornberger, C.-A.: Halsneurinom. Acta oto-lar. 116: suppl., pp. 205-211 (1954). Martin, H. and Romieu, C.: The diagnostic significance of a lump in the neck. Postgrad. Med. 11: 491-500 0952). Reddick, L.P. and Myers, R.T.: Neurilemmoma of the cervical portion of the vagus nerve. Am. J. Surg. 125: 744-747 (1973). Russell, D.S. and Rubinstein, L.J.: Pathology of tumours of the nervous system (Arnold, London 1971). Skucas, J.; Rossi, P.: Brinker, R.A., and Eberle, R.C.: Angiographic differentiation of neuro genic tumors at the carotid artery bifurcation. Surgery Gynec. Obstet. 137: 35-39 (1973). Slaughter, D.P. and dePeyster. F.A.: Pharyngeal neurilemmomas of cranial nerve origin. Archs Surg. 59: 386-397 (1949). Stout, A.P.: The peripheral manifestations of the specific nerve sheath tumor (neuri lemoma). Am. J. Cancer 24: 751-796 (1935). Verocay, J.: Zur Kenntnis der Neurofibrome. Beitr. Pathol. 48: 1-69 (1910). Violé, P.: Schwannoma of the pharynx. Ann. Otol. Rhinol. Lar. 55.' 334-341 (1946). Waggener, J.D.: Ultrastructure of benign peripheral nerve sheath tumors. Cancer 19: 6 9 9 709 (1966).
