Auckland’s Neurogenic Thoracic Outlet Syndrome Specialist
People with neurogenic thoracic outlet syndrome (nTOS) usual have a history of neck injury (e.g. whiplash etc.) which can result in injury or tears to the scalene muscles in the neck and thoracic outlet. As the injury heals, the damaged muscle can form scar tissue either within or adjacent to it. This muscle fibrosis process is often the cause for compression of the nerves of the brachial plexus which results in the neurogenic TOS.
There are other predisposing factors to nTOS, including anomalous cervical ribs, congenital ligaments or bands compressing or impinging on the nerves or nerve roots, narrow scalene triangle or muscle anomalies (variations of the scalene minimus), all of which can cause nTOS. While the first rib (not cervical rib) is in itself not directly responsible for nTOS, it can contribute to the problem by allowing scar tissue to compress the nerves against it. A cervical (complete or incomplete) rib occurs in up to 5% of patients with thoracic outlet syndrome and can form an attachment to the first rib, either through a band of cartilage, tendinous or bony fusion.
What are the primary symptoms of nTOS?
The main symptoms of nTOS occur predominantly in the affected arm or hand and can cause pain, discomfort, numbness or weakness. The symptoms are usually not localised to one particular nerve or nerve distribution and can involve any part of the entire arm, neck or even part of the upper back. Activities that involve sustained or repetitive actions, especially those where there is elevation of the arm or repeated turning of the neck (e.g. prolonged typing on a keyboard, driving a car, brushing hair, hanging up the washing etc.), can cause strain and scarring of the scalene muscles which may potentiate potential compression of the underlying nerve roots by narrowing the scalene triangle
Neurogenic thoracic outlet syndrome can also manifest as headaches usually occurring as a result of referred pain to the back of the head because of secondary spasm within the trapezius and paraspinous muscle. Prolonged, severe extrinsic compression of peripheral nerves can result in muscle weakness and atrophy, but such findings are actually rare in patients with nTOS – due to intermittent nature of nerve compression in neurogenic thoracic outlet syndrome.
How is neurogenic thoracic outlet syndrome diagnosed?
Examination involves a thorough musculoskeletal and neurological assessment of the neck and upper limb. Occasionally, “trigger points” may be present within the scalene muscle that re-create the patient’s symptoms of pain and numbness. If identified, this is a useful manoeuvre as it serves to reinforce the diagnosis of nTOS. The EAST test may also be performed where the arms are held up above the head and the patient opens and closes their fists repeatedly. In those patients where the symptoms occur soon after starting this test, the diagnosis of nTOS is reinforced.
Diagnosis of neurogenic thoracic outlet syndrome can be quite difficult and rests mainly on pattern recognition of clinical symptoms. There is no single imaging or diagnostic test that accurately diagnoses or excludes nTOS however, there is a strong correlation between a positive scalene block and good response to surgery. Non-invasive cross-sectional imaging (e.g. MRI) is useful to exclude any other obvious causes of nerve compression in and around the thoracic outlet. Nerve conduction studies are often negative because nerve compression happens very proximally. Plain X-rays of the neck are useful to exclude a cervical or bony rib abnormality. Scalene muscle block is perhaps the most useful diagnostic test, where local anaesthetic is injected into the anterior scalene muscle around the brachial plexus. If the patient experiences a relief in their symptoms following this procedure, the chances of success of thoracic outlet decompression surgery are much higher.
What type of treatment is available?
Once diagnosis is confirmed, treatment initially consists of physiotherapy with the aim of correcting any posture, alignment and movement abnormalities of the neck, shoulder and upper limb. If there are not significant abnormalities found during physical therapy, then surgical options are considered, specifically, excision of the scalene muscle (scalenectomy) along with any other muscular variants compressing the brachial plexus. The need to excise the first rib is a highly debated topic, with good response achieved in those who have had as well as those who haven’t had first rib resection along with scalenectomy. In those patients where the symptoms are long-standing or there is a lack of response to scalene muscle block, the outcomes of surgery are poorer.
Contact Mr. Venu Bhamidi today for an appointment
If you believe that you may be suffering from thoracic outlet syndrome, book a consultation with Mr. Venu Bhamidi today. To book an appointment, please call today on 0800 82 72 37 or complete an enquiry form on our contact page.