Schwannomas arise from the Schwann cells and are common benign neoplasms of the peripheral nerves. In our series we present our experience of surgical treatment and analysis of results of excision of schwannommas.Clinical material consisted of 6 patients, amongst them 7 schwannomas located in the upper extremities were excised between 2014 and 2016.Five tumours had origin from major peripheral nerves and two from the small nerve branches. In the post-operative period pain resolved in all the patients, paraesthesia in 4 and motor function in 5, partial in 1.Sensory function improved in 4 and partial in 2 which later improved completely. Median [2] and ulnar [3] nerves were the commonly affected peripheral nerves. Small nerve branch Schwannomas were identified the site of origin and carefully removed. Definitive healing achieved in all the cases. Conclusions; Schwannomas predominantly arise from ulnar and median nerves in the upper extremity. Slow growth of the tumour causes compression neuropathy of varying degrees which is an indication for surgery. Improvement in the function of the peripheral nerve achieved after excision of the schwannomas. The risk development of permanent post-operative neurological deficit is very low.
1.Introduction
Schwannomas were described by Verocayin in 1908 as benign neoplasms of the peripheral nerves. Schwannomas occur in the third and fifth decades of life without racial or gender preponderance. They develop as solitary tumours varying from 1~3cms in diameter although rare and multiple tumours have been described. Upper extremity schwannomas account for 12 to19% and are located mostly on the volar surface. Schwannomas constitute 8% of all the soft tissue tumours and are composed entirely of Schwann cells. They are slow growing well encapsulated tumours and have a non-infiltrating growth pattern. Expanding tumour mass displaces nerve fascicles .Clinical symptoms are attributed to the compression of the nerve fascicles. Magnetic resonance imaging is the preferred diagnostic tool, and on image scan, tumour presents as well defined fusiform mass within the nerve. They look isointense to surrounding muscles on T1 –weighted images and hyper intense on T2 weighted images on intravenous administration of contrast medium neurogenic tumours show signal enhancement. Many authors agree that on the basis of MRI findings it is difficult to differentiate between malignant and benign tumours as well as between different types of benign tumours. Histopathologically schwannomas contain two different areas of varying proportion. Highly cellular composed of spindle cells which form palisade and produce Verocay bodies are called Antoni type A area. Mucinous matrix with loosely arranged Schwann cells are described as Antoni type B area. In most of the tumours one area will be predominant over the other area. Rare variants of schwannomas are cellular, epitheloid melatonin, and plexiform type. Monoclonal antibodies are used against proteins;S100,CD31,CD34 and GFAP in the immunohistochemical analysis in differential diagnosis of the peripheral nerve tumours. Aim of this work is to present our experience in the management of upper extremity schwannomas and analyse the surgical results and the risk of development of new postoperative neurological deficits.
2. Material and methods;
Clinical material consisted of 3 males and 3 females; age of the patients was from 16 to 72 yrs. with average of age 42.5 yrs. All patients were operated on for Schwannomas located in the upper extremity between 2014 and 2016.The patients were scheduled for operation on the basis of clinical examination and diagnostic imaging findings and presence of symptoms such as pain, positive Hoffmann-Tinel sign, sensory impairment and motor deficits.Preoperatve evaluation was done for anamnesis, physical examination of tumour sensory function testing (pain, touch static and dynamic sensory discrimination) muscle tone, and strength examination and as well as testing for Hoffman –Tinel sign. To evaluate the sensory function and muscle strength of the upper extremity modified BMRC scale was used Surgical treatment results were evaluated using the scales metioned above.Post operative follow up period was1.5 to 2yrs.
3.Resuts;
3.1 Location of the tumours; Schwannomas were located in the right upper extremity in 6 patients and one in left upper extremity. In total of 6 patients 7 tumours were excised. Most of the Schwannomas originated from the major peripheral nerves, 3 from ulnar nerve 2 from median nerve and 2 from the digital nerves. Two tumours from ulnar nerve at level of wrist one proximal to wrist were removed. Two tumours from Median nerve distal to elbow were removed. Two tumours from the digital nerves of the ring and middle fingers excised
3.2 Preoperative Examination in the group of tumours arising from major peripheral nerves revealed positive Hoffman-Tinel sign and paraesthesia in 4 out of 5 patients. Pain was present in 4 out of 6 patients. Pain was triggered by applying pressure to tumour in 3 patients, one patient suffered from night pain. Superficial sensory function disturbance was detected in 2 out of 6 patients, and motor deficit in 1 out of 6 patients.
3.3. Histopathological reports in all of the excised and examined tumours showed pattern of typical schwannomas, tumours from the small nerve branches had histopathological pattern of classical schwannomas( plexiform schwannomas).
3.4,Post-operative evaluation Results; Recurrence was not observed in any of the patient in the follow up period. Pain resolved in 5 patients, No relationship observed between the presence of pain and the size of the tumour. Paraesthesia resolved in 4 patients who had suffered from it preoperatively Hoffman-Tinel sign was negative in the post-operative course New neurological deficit was observed in one patient. The tumour arising from the small nerve branches excised in one piece with identification of the site of origin. After removel of tumours, definitive healing was achieved.
4. Discussion; In our study schwannomas originated from the major peripheral nerves of the upper extremity. The common site of origin was ulnar, median and small nerves. After analysis of data from three major clinical centres, comprising of 72 cases,, Siquera et al., described 12 cases had origin from ulnar nerve 12 cases from median nerve and 3 cases from radial nerve. Date et al, observed tumours of the upper extremity in descending order of frequency in ulnar median and radial nerves in the clinical material consisted of 36 cases of schwannomas. The site of rare location of schwannomas is musculocutaneous nerve described by these authors. Adani et al., established the most common site of origin of tumour in descending order of frequency are ulnar n(14) median n(3) musculocutaneous nerve 3 and digital nerves 3 tumours. In our study none of the tumours located in the axillary or musculocutaneous nerve. Tumours arising from the small nerve branches were located in the and the schwannomas arising from the major peripheral nerves were evenly distributed along the length of the upper extremity. Schwannomas mostly develop as solitary tumours, their growth is eccentric and non-infiltrating can often be excised with or with only minimal damage to the fascicular structure. Adani et al., in 2008 published an article comprising 24 cases of upper extremity schwannomas; they were able to excise 20 tumours without damage to the fascicular structure. The risk of developing new post-operative neurological deficit is always a possibility in traumatic tumour excision. Their causative factors are diverse, Firstly possibility of damage to the fascicles encircling the tumour during incision of the epineurium to be considered. Compression or irritation of the fascicles during dissection can cause nerve function impairment. Park et al., concluded that transection of the fascicles during dissection of the tumour may result in new postoperative neurological deficits. Donner et al.,on the contrary has opined that fascicles entering the tumour are non-functional and their transection does not cause additional neurological deficit The incidence of neurological deficiency after removal of schwannomas varies between 1.5 to 80 per cent. Significantly High percentage of complications occurs in the short term period observations. Adani et al., described worsening of paraesthesia’s in 23 out of 24 patients In the early post-operative period which spontaneously resolved in al the patients within 12 months from the operation.Siqueira et al, reported postoperative complication rate of 15.2 %( 11out of 72 operated on patients). Majority of the reported deficits were transient eventually sensory impairment in 3 patients and motor deficit in1 patient was observed out of 72 patients. Kim et al presented series of 30 schwannomas of the lower extremity with a complication rate in the early postoperative period was 76% and the neurological deficit in 2 of the operated on patients. Kang et al., published in 2000 with permanent sensory impairment in 1 out of 20 patients in his series. . Similarly, Knight et al observed .serious post-operative complications in 5 out of 198 treated patients. In our study neurological deficit was observed in one patient post operatively which improved completely in the follow up period of 6 months. During final clinical evaluation of our patients we observed no new neurological deficit; at most there was no improvement in certain neurological functions that had been impaired during preoperative evaluation. It has been confirmed several studies that schwannomas can rarely impaired motor function. Neural tumours producing motor deficit should always arise a high suspicion of malignancy. In our opinion patients with benign tumours may also show motor impairment preoperatively.
5. Conclusions (1) Schwannomas in upper extremities predominantly arise from major peripheral nerves, most common nerve of origin ulnar nerve and the median nerve.(2) the risk of exacerbation of compression neuropathy caused by gradual tumour growth justifies surgical excision in symptomatic nerve tumours.(3) with the use of adequate operative techniques in most cases improvement in peripheral nerve function after the excision of schwannomas achieved. (4)The risk of development of new permanent post-operative neuro logical deficit is low.