Scratch Collapse Test Is a Useful Clinical Sign in Assessing Long Thoracic Nerve Entrapment

The Scratch Collapse Test in patients diagnosed with Anterior Cutaneous Nerve Entrapment Syndrome (ACNES): A report of three cases

INTRODUCTION AND IMPORTANCE

The Scratch Collapse Test (SCT) is currently used as a supportive tool diagnosing peripheral nerve neuropathies including carpal tunnel syndrome or peroneal nerve entrapment. Some patients with chronic abdominal pain suffer from entrapment of terminal branches of intercostal nerves (anterior cutaneous nerve entrapment syndrome, ACNES). ACNES is characterized by a severe disabling pain at a predictable area of the anterior abdomen. Clinical examination shows altered skin sensation and painful pinching at the area of pain. However, these findings may be subjective.

CASE PRESENTATION

In three female patients aged 71, 33, and 43 years with suspected ACNES, the SCT was positive when scratching over the skin of the affected nerve-ending at the abdominal wall. The diagnosis ACNES was confirmed with a local abdominal wall infiltration at the tenderpoint in all three patients. In case three, the SCT turned negative after lidocaine infiltration.

CLINICAL DISCUSSION

ACNES was hitherto a clinical diagnosis just based on clues in medical history and physical examination. Performing a SCT in patients possibly having ACNES may additionally contribute to the diagnosis.

CONCLUSION

The SCT may serve as an additional tool for diagnosing patients with possible ACNES. A positive SCT in patients with ACNES supports the hypothesis that ACNES is indeed a peripheral neuropathy of terminal branches of the lower thoracic intercostal nerves. Controlled research is necessary to confirm the role of a SCT in ACNES.

Validity of Using the Scratch Collapse Test in the Lower Extremities

BACKGROUND

The scratch collapse test is a provocative test that has been successfully used for peripheral neuropathies. The elbow is the main testing site, but there may be times when use of the upper extremities is contraindicated. This study sought to determine the sensitivity of using the scratch collapse test on the lower extremity for upper extremity neuropathies.

METHODS

One hundred patients with an electromyographically confirmed diagnosis of carpal tunnel or cubital tunnel syndrome were prospectively enrolled. As a control, the scratch collapse test was conducted normally using the elbow as a testing site. After a baseline was established, the test was repeated using eversion of the foot and ankle against an inversion force.

RESULTS

Of the 100 study patients, 89 had a positive scratch collapse test on the upper extremity and 84 had a positive test on the lower extremity. In the 51 patients with carpal tunnel syndrome, 45 had a positive test on the upper extremity (sensitivity, 88.2 percent; 95 percent CI, 76.13 to 95.56 percent), and 42 had a positive test of the lower extremity (sensitivity, 82.35 percent; 95 percent CI, 69.13 to 91.60 percent). In the 49 patients with cubital tunnel syndrome, 44 had a positive test on the upper extremity (sensitivity, 89.8 percent; 95 percent CI, 77.77 to 96.6 percent), and 42 had a positive test on the lower extremity (sensitivity, 85.7 percent; 95 percent CI, 72.76 to 94.06 percent).

CONCLUSION

There were no statistically significant differences in the sensitivities of the scratch collapse test on the upper or lower extremities, suggesting that the lower extremity could serve as an alternative site for the scratch collapse test.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Diagnostic, II.

The scratch collapse test: A systematic review

The diagnosis of nerve compression relies on collecting diagnostic clues from the history, physical examination, imaging and diagnostic testing. There are several provocative tests to aid in the diagnosis of nerve compression. The 'Scratch Collapse Test' (SCT) has emerged as a new provocative test to assist in the localisation of peripheral nerve compression. This study aims to perform a systematic review of literature to assess the data on the reliability of the SCT as a diagnostic test for entrapment neuropathy. Ten articles were reviewed. Five articles had sufficient numerical data for analysis, and in these five articles, the positive predictive values and specificity were high, i.e. between 0.71 and 0.99 and 0.6 and 0.99, respectively, whereas other values were very variable, i.e. individual negative predictive values ranged from 0.15 to 0.92 and the sensitivity values ranged from 0.24 to 0.77. Another main finding was the versatility of the test in that it can be used for various nerve entrapments and to localise the exact level of compression. Literature suggests that SCT has potential to be used as a clinical diagnostic tool for entrapment neuropathy. However, wide variations in early literature suggest that SCT should not be used as a sole diagnostic tool but as an adjunct to a surgeon's diagnostic repertoire.

Surgical and Clinical Decision Making in Isolated Long Thoracic Nerve Palsy

BACKGROUND

Isolated long thoracic nerve palsy results in scapular winging and destabilization. In this study, we review the surgical management of isolated long thoracic nerve palsy and suggest a surgical technique and treatment algorithm to simplify management.

METHODS

In total, 19 patients who required surgery for an isolated long thoracic nerve palsy were reviewed retrospectively. Preoperative demographics, electromyography (EMG), and physical examinations were reviewed. Intraoperative nerve stimulation, surgical decision making, and postoperative outcomes were reviewed.

RESULTS

In total, 19 patients with an average age of 32 were included in the study. All patients had an isolated long thoracic nerve palsy caused by either an injury (58%), Parsonage-Turner syndrome (32%), or shoulder surgery (10%); 18 patients (95%) underwent preoperative EMG; 10 with evidence of denervation (56%); and 13 patients had motor unit potentials in the serratus anterior (72%). The preoperative EMG did not correlate with intraoperative nerve stimulation in 13 patients (72%) and did correlate in 5 patients (28%); 3 patients had a nerve transfer (3 thoracodorsal to long thoracic at lateral chest, 1 pec to long thoracic at supraclavicular incision). In the 3 patients who had a nerve transfer, there was return of full forward flexion of the shoulder at an average of 2.5 months.

CONCLUSIONS

A treatment algorithm based on intraoperative nerve stimulation will help guide surgeons in their clinical decision making in patients with isolated long thoracic nerve palsy. Intraoperative nerve stimulation is the gold standard in the management of isolated long thoracic nerve palsy.

Scratch Collapse Test for Carpal Tunnel Syndrome: A Systematic Review and Meta-analysis

Background:

Despite the fact that carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, the diagnostic accuracy of clinical screening examinations for CTS is controversial. The scratch collapse test (SCT) is a novel test that may be of diagnostic advantage. The purpose of our study was to determine the diagnostic accuracy of the SCT for CTS.

Methods:

A literature search was performed using PubMed (1966 to April 2018); Ovid MEDLINE (1966 to April 2018); EMBASE (1988 to April 2018); and Cochrane Central Register of Controlled Trials (The Cochrane Library, to April 2018). We examined the studies for the pooled sensitivity, specificity, and likelihood ratios of the SCT. This review has been registered with PROSPERO (CRD42018077115).

Results:

The literature search generated 13 unique articles. Seven articles were included for full text screening and 3 articles met our inclusion criteria, all of which were level II evidence with low risk of bias (165 patients). Pooled sensitivities, specificities, positive likelihood ratio, and negative likelihood ratios were 0.32 [95% CI (0.24–0.41)], 0.62 [95% CI (0.45–0.78)], 0.75 [95% CI (0.33–1.67)], and 1.03 [95% CI (0.61–1.74)], respectively. The calculated area under the summary receiver operating characteristic (AUSROC) curve was 0.25, indicating a low diagnostic accuracy.

Conclusion:

The SCT has poor sensitivity; however, it is moderately specific. Based on the current literature and their variable quality of the evidence, we conclude that the SCT is not an adequate screening test for detecting CTS.