Sural sparing in Guillain–Barré syndrome subtypes: a reappraisal with historical and recent definitions
Introduction
Although not formally included to date in any set of electrodiagnostic criteria, sensory nerve conduction studies are routinely performed for suspected Guillain–Barré syndrome (GBS). Few studies of sensory abnormality patterns have been conducted in inflammatory neuropathies. One of the reported features is that known as the “sural sparing” pattern which has been described as being suggestive of acute and chronic demyelinating neuropathies (Bromberg and Albers, 1993, Al-Shekhlee et al., 2005). Other studies demonstrated the utility of median/radial and sural/radial ratios in different neuropathy subtypes (Rutkove et al., 1997, Tamura et al., 2005) as well as comparative radial/sural amplitude patterns (Rajabally and Narasimhan, 2007).
Definitions of “sural sparing” have however been variable and multiple. Earlier studies have used the “abnormal median normal sural” pattern (Bromberg and Albers, 1993), or “normal or relatively preserved sural sensory nerve action potential (SNAP) compared with at least two abnormal SNAPs in the upper limb” (Al-Shekhlee et al., 2005). “Extreme” patterns comprising an absent median but preserved sural response were described over twenty years ago and found highly specific for acute inflammatory demyelinating polyneuropathy (AIDP) and chronic inflammatory demyelinating polyneuropathy (CIDP) (Bromberg and Albers, 1993). The usefulness of the “sural sparing” sensory abnormality pattern in diagnosing GBS has recently been further evaluated and found to be the most specific finding in distinguishing GBS from its mimics in a multicentre study (Derksen et al., 2014). The definition used in this study however was of a “spared” or present, normal sural response with an abnormal ulnar SNAP. Although initially described as a feature of demyelinating neuropathy, and therefore, of the AIDP form in GBS, sural sparing has also been reported in Miller Fisher syndrome (MFS) and found in some patients with acute motor axonal neuropathy (AMAN) (Umapathi et al., 2012, Umapathi et al., 2014, Sekiguchi et al., 2013, Capasso et al., 2011). A more recent analysis has suggested that sural sparing, which the authors defined as relative greater sensory potential amplitude reduction of median or ulnar versus sural nerves, was as frequently found in AIDP as in axonal forms of GBS and therefore not indicative of demyelinating pathology (Umapathi et al., 2015). Whether this finding is applicable to other possible definitions of sural sparing, to the use of different electrophysiological criteria for GBS and to electrophysiological studies performed in the early disease stages, when the findings can be truly diagnostically useful, is currently unknown. These many uncertainties about the significance of sural sparing in GBS prompted us to conduct this current analysis.
Section snippets
Methods
We retrospectively reviewed our institutional database of patients admitted with a diagnosis of GBS between 2001 and 2012 at the Queen Elizabeth Hospital, Birmingham, UK. The diagnosis was made in each case in accordance with established clinical criteria (Wakerley et al., 2014). Included patients had undergone electrophysiological testing of at least 3 motor and 2 sensory nerves (consisting of at least one upper limb and one sural nerve) within 21 days of symptom-onset. Electrophysiology was
Results
We included 78 consecutive patients with a diagnosis of GBS, seen at the Queen Elizabeth Hospital, Birmingham, between 2001 and 2012. Patients were excluded on the basis of incomplete clinical details, delayed electrophysiology performed <21 days after disease onset or insufficiently exhaustive electrophysiology and a subsequently confirmed diagnosis of acute-onset CIDP. There were 52 males and 26 females. Mean age was 51.0 years (S.D.: 17.8). Mean interval from disease onset to nerve conduction
Discussion
Our findings demonstrate heterogeneity depending on the definition used for sural sparing. We chose to study all the different sensory abnormality patterns as they covered the 2 recent definitions used in the literature as well as previous definitions, including original descriptions (Bromberg and Albers, 1993, Al-Shekhlee et al., 2005, Al-Shekhlee et al., 2007, Rajabally and Narasimhan, 2007, Derksen et al., 2014, Umapathi et al., 2015).
In order to assess the relevance of relative lower limb
Funding
None.
Conflict of interest
None declared in relation to this work.
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