Subclavian Steal Syndrome
The following case study was a patient that presented in clinic in the year in which I considered Subclavian Steal Syndrome (SSS) within my differential diagnosis. (SSS) is an interesting presentation intertwined within a number of other pathologies that can muddy the water. The following case study looks to give you another area to consider when your index of suspicion doesn’t quite fit. A special thanks to Alan Taylor for the initial advice and support, who is a wealth of knowledge on Haemodynamics. Check out his chat with Jack Chew and the podcast on Haemodynamics
SSS involves a proximal subclavian stenosis, which results in a lower pressure in the distal subclavian artery. The vertebrobasilar circulation is a closed hydraulic system, so this pressure difference creates a retrograde flow, pulling blood from the contralateral vertebral artery to the basilar and then down the ipsilateral vertebral artery, “stealing” from the cerebral circulation (Williams et al, 1936; Lord et al, 1969; Berger et al, 1967). This flow reversal has been classified as complete or incomplete meaning that the flow reversal is ‘Continuous’ vs. ‘Intermittent’ (Berger et al, 1967; Bornstein & Norris, 1986), with the latter reproducing the subclavian steal phenomena. However, it is the continuous flow reversal that will be responsible for the majority of the true syndromes (Berger et al, 1967). We know that the vertebral artery serves as an important collateral circulation to the upper extremity, therefore this same mechanism may lead to arterial insufficiency and symptomatology from the arm. In such cases, patients may have atypical presentations with weakness of the arm and hand, cool temperature, and paresthesia (Chan-Tack, 2001). The siphoning or “stealing” of blood has traditionally been thought to cause symptoms of vertebrobasilar insufficiency, such as transient ischemic attacks (TIA), vertigo, dizziness, syncope, or presyncope following exercise of the upper extremity. Some of the other signs and symptoms that you may encounter during the subjective assessment may also include, weakness, clumsiness of an extremity, loss of vision, homonymous hemianopsia, ataxia, drop attacks and arm claudication following exercise. Another nice one to be aware of is that these signs and symptoms may also be associated with a reduced blood pressure of greater than 20 mmHg with reduced or absent radial pulse of the affected arm (Fernando et al 2013, Kesteloot 1963). However, the true prevalence of this syndrome is still unknown and has been estimated by authors from small or single center studies to be between 0.6% and 6% (Labropoulos et al 2010; Boodth 1979). The controversy is generated due to 80% of patients demonstrating flow reversal phenomenon that are asymptomatic with most patients presenting with symptoms that will have concurrent cerebrovascular lesions (Klingelhöfer et al 1988). As with most complex pathologies, it can present with a myriad of neurological and vascular signs and symptoms, but most commonly presents as an incidental finding in an asymptomatic patient (Kesteloot 1963). The left subclavian artery has a more prominent angle at its origin, therefore turbulent flow will accelerate atherosclerosis and account for more than 80% of the cases. In contrast, there is only a small number of patients that present with right sided symptoms and even fewer with bilateral (Labropoulos, et al 2010) Several other etiologies have been described as secondary causes of stenosis, most of them post surgical intervention, post radiation, congenital abnormalities, trauma, arteritis, and thoracic outlet syndrome (TOS) (Nguyen et al, 1997; Lee & Seo, 2003)
A 51-year-old female presented with a 2-year history of insidious left sided posterior peri-scapular shoulder pain (VAS 8) with progressive radicular symptoms through a C5-T1 distribution over the last 6 months with the following reported during questioning:
- Altered sensation across the left side of the face
- Intermittent left sided blurred vision
- Light-headedness with left upper arm activity > 90 degrees ROM
- Intermittent loss of fine motor control associated with picking up small objects and deterioration in their handwriting.
- Nausea associated with shoulder movement above 90 degrees of abduction and/or flexion
- ‘Heaviness’ of the upper limb, particularly with exercise
- Insidious and progressive, Shortness of breath (SOB) within the last 2- weeks
- SOB on walking up inclines, as well as upper limb activity above 90 degrees (ROM)
The following were reported as normal or negative:
- No bladder and bowel changes
- No Thyroid concerns or history of Cancer
- Stable weight
- No signs of infection/fever
- No Malaise
- No night pain
- Gait was unremarkable
- No recent trauma *
The signs and symptoms described raised the index of suspicion during the work up of the subjective assessment to consider serious underlying pathology. The pattern of symptoms and distribution are described in the literature as being present with Thoracic Outlet Syndrome (TOS), Subclavian Steal Syndrome (SSS) and sinister pathologies such as Pancoast Tumor and Upper Limb Extremity Deep Vein Thrombosis (ULEDVT) (Sanders et al, 2007). As you can see which ever way you go, there are clinical challenges and decisions! Nice case study here from Adam Meakins on ULEDVT as well.
The patient was working in a high-powered job in the city for the last 3 years, which was described as stressful and was looking to move job roles to reduce stress levels and spend more time with their family. Past medical history included hypertension for the last 2-years for which they were under their (GP) and we know from the literature that one of the risk factors for this syndrome includes hypertension and hypercholesterolemia (Reivich et al, 1961; Rutherford, 1984; Sabiston, 1987; Harper & Haines, 1988; Sagkaguchi, 1955; Kapoor, 1990). The patient was also a Type II diabetic which was described as being stable.
The patient described a soft tissue injury (STI)* to the left shoulder whilst lifting a box three years ago that subsequently required admission to hospital for pain control over a 3-day period (bit extreme…I know!), however could be relevant. In light of this, consideration for postural adaptations post STI and compromise to the Thoracic Outlet could have been a contributing factor and has been described as potential sources of TOS encroachment (Hachulla et al., 1990; Rayan and Jensen, 1995). The patient had also been seen by a number of practitioners prior to assessment as well as currently being under the care of a Consultant for ongoing headaches for which they had recently received an MRI of the head and cervical spine. The MRI was reported as ‘unremarkable cervical spine with no vascular abnormalities reported on the MRI of the head…’
The initial concern was the insidious onset of (SOB) alongside the other flags mentioned and cardiac involvement and sinister pathology such as Pancoast Tumor, Pulmonary Embolism and UEDVT required consideration during the work up.
On examination the patient stood with a protracted and elevated left shoulder joint, which could be attributed to the STI to the left shoulder. There was no visible signs atrophy, abnormalities, skin discolouration, signs of swelling or rash of the upper limb or surrounding musculature. A full neurological examination was carried out, including cranial nerve testing, Pronator Drift, Hoffman’s, Rapid Arm Movement (RAM) co-ordination and dexterity tests. All reflexes for the upper and lower limb were recorded as normal with C5-T1 deficit in dermatomes moted as (3/5) and a muscle power reduction (2/5) at C2-5 when compared to the right. Now, I know some may say they wouldn’t have done a full neuro, but the other consideration lingering in the back of my mind was an underlying Myelopathy so ‘Rule in’ and ‘Rule out’ was my primary goal and the integrity of the spinal cord was not reported on during the recent MRI.
Range of Movement (ROM) of the left shoulder into abduction above 90-degrees caused ‘heaviness’, increase in radicular symptoms and light headedness that all resolved when the arm was retuned to beneath 90 degrees of abduction. Neurogenic TOS (NTOS) was considered during the differential diagnosis as it is characterized by compression of neurovascular structures as they pass through the thoracic outlet and affects approximately 8% of the population, with a female to male ratio of up to 4:1 (Roos DB, 1976). Almost all cases of TOS (95-98%) affect the brachial plexus, with the other 2-5% affecting vascular structures, such as the subclavian artery and vein (Nichols A, 2009).
The differential diagnosis between TOS and SSS is a real challenge as there is no one single test to confirm their presence. Variable presenting symptoms complicated by multiple anatomical anomalies, present a diagnostic dilemma. Therefore it is considered that diagnosis is usually confirmed by a combination of a detailed history and physical examination coupled with relevant investigations with appropriate clinical justification (Hooper et at, 2010). Roos stress test – EAST test (elevated arm stress test) and Adsons Manoeuvre was used to confirm TOS compromise (+/-) SSS, which highlighted symptoms of weak radial pulse, fatigue, burning sensation and paresthesia into the hand indicating a positive test, however the literature on sensitivity and specificity for objective testing can be questionable (Lee et al; 2006, Roos, 1976, Walsh, 1994, Hachulla et al., 1990).
The examination findings were of a complex nature with a multitude of variables to consider. The presentation of radiclaur symptoms with pain and heaviness in the left arm with intermittent loss of dexterity when picking up small objects, SOB on exertion and facial pain was sufficient to raise the index of suspicion towards a potential serious pathology.
The initial management was:
Discussion with a Consultant resulted in agreement for referral for plain chest x-ray and bloods to rule out signs of infection and sinister pathology alongside Duplex ultrasound. The Duplex Ultrasound is considered as non-invasive and has a high sensitivity and specificity for peripheral presence and grade of SSS of and is seen as the initial imaging test of choice (Warren and Burke 2011).
Results and outcome:
Bloods and chest x-ray were reported as normal and Duplex Ultrasound highlighted a Grade II Subclavian Steal with intermittent, partial, latent, alternating and antegrade flow in the diastolic phase and retrograde flow in the systolic phase, which was in line with some of the reported literature (Osrio et al, 2012). The patient was managed with a conservative approach and started on antiplatelet therapy, aggressive lipid management, review of hypertensive medication and diabetic review alongside life style modifications (Fernando et al 2013). On follow up the patient reported a reduction in the ‘heaviness’ within the upper limb with SOB being less on exertion and neurologically the dermatomal/mytomal pattern was improving with handwriting much improved with greater control. Admittedly it is early days for the patient and they have a Consultant follow up in late September.
The case presentation hopefully demonstrates a complex pathology with a number of flags and symptoms that required consideration in relation to the index of suspicion and management plan. Although we don’t come across them that often, there are a lot of familiar signs and symptoms that cross over into a variety of clinical presentations, so always good to have an awareness of vascular complications and presentations that can masquerade as other pathologies.
As always, thanks for reading.
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