Radiologist Identification of Occult Dorsal Wrist Ganglion Cysts on MRI

Abstract

Background  Occult dorsal ganglion cysts (ODGC) require imaging or an operation for detection. It is currently unknown how often a radiologist identifies an ODGC on magnetic resonance imaging (MRI) and whether surgeon indication for MRI aids the radiologist in detection.

Questions/Purposes  The aim of the study was to investigate the following questions: how accurately do radiologists identify ODGC on MRIs? What factors may be associated with missed ODGCs?

Patients and Methods  We retrospectively studied patients who underwent an operation for an ODGC and had a preoperative wrist MRI. Radiology report and surgeon's notes were evaluated to determine whether identification of the ODGC was noted and whether the surgeon indicated that the MRI was to evaluate for an ODGC. MRIs were reviewed, dimensions of cysts measured and volume of cyst calculated.

Results  Twenty-four patients and 25 MRIs were analyzed. The radiologist identified the ODGC in 19 cases (76%). Fifteen of the 25 MRIs (60%) ordered had ODGC listed in the requisition comment by the ordering surgeon. Thirteen of these 15 (87%) ODGCs were seen by the radiologist. Ten of the 25 MRIs (40%) ordered did not mention ODGC in the requisition. Six of these 10 (60%) ODGCs were seen by the radiologist. The volume of the ODGCs missed by radiologists was smaller (mean, 0.049 cm ³ ) than those the radiologists identified (mean, 0.31 cm ³ ; p  = 0.004).

Conclusions  Radiologists will not always identify the ODGC on an MRI, but they were more likely to if the surgeon was concerned for one. Hand surgeons should report suspicion of an ODGC on MRI requisition and review all imaging independently.

Level of Evidence  This is a Level III, prognostic study.

Ganglion cysts are fluid filled cysts with a stalk connecting it to the synovial membrane of the scapholunate ligament. ¹ They are the most common mass in the wrist, typically found on the dorsal aspect, although some studies have seen a higher percentage of ganglion cysts in volar than dorsal wrist in asymptomatic individuals. ^{2 3} The exact pathogenesis of these cysts is currently unknown but believed to be due to a one-way valve formation that allows fluid into the cyst but not back out. ⁴ While the majority of ganglion cysts are asymptomatic, they can be a cosmetic complaint, worrisome to the patient that it is malignant growth, or even be painful and debilitating, especially with gripping strength and direct pressure on the wrist. ^{5 6} First-line treatment is observation since the cysts can recede on their own. ⁷ Interventional treatment includes aspiration and open or arthroscopic cyst removal. ^{8 9}

Diagnosis of a ganglion cyst is largely clinical, but sometimes magnetic resonance imaging (MRI) or ultrasound is used for definitive diagnosis, or when the clinician is evaluating wrist pain of unknown etiology. An occult dorsal ganglion cyst (ODGC) is one that is not clinically observed or palpated but is found on imaging studies or intraoperatively. Previous studies have solely investigated the ability of MRI to detect occult ganglion cysts. One study included 14 patients and another study included 20 patients, with the results showing that not all cases of occult ganglion cyst that were later diagnosed intraoperatively or histologically were identified on MRI. ^{10 11} However, in these studies, the accuracy of the MRI in identifying an ODGC was dependent on the radiologist report only and did not discuss the surgeon's review of the same MRI.

The purpose of this study was to determine how accurately radiologists identify ODGCs on MRIs and what factors may be associated with missed ODGCs by radiologists. With this work, we hope to make recommendations to hand surgeons to improve their ability in diagnosing possible ODGCs as the source of a patient's wrist pain.

Materials and Methods

After obtaining institutional review board approval, a single-center retrospective chart review of patients from January 01, 2011, to January 31, 2017, was performed. Individuals who underwent an operation and had at least one of the following billed CPT (current procedural terminology) codes: 25111, 25040, 26116, 29844, 25101, and 25105 were identified via query of the patient database. Subsequently each patient's chart underwent review for possible inclusion in the study. Inclusion criteria were that one of the procedures performed during the operation must've included excision of a dorsal ODGC, the clinic notes should not have mentioned either a visible or palpable dorsal cyst, an MRI must have been ordered and obtained, and the existence of an ODGC must've been confirmed by the surgeon (intraoperatively). The exclusion criteria were charts that did not have an ODGC and those charts that had an ODGC but the MRI report or images were not available.

Once the individuals with an ODGC were identified, we then reviewed the MRI requisition and checked whether a reason for the MRI was noted. If the reason included the words “occult dorsal ganglion cyst,” “ganglion,” or “cyst” that chart was designated as a “1,” but if the reasoning for the MRI did not include these words, that chart was designated as a “0.” The MRI report written by the radiologist was also reviewed. If there was mention of a “ganglion,” “cyst,” or “occult dorsal ganglion cyst” in the report, then this was a confirmed ODGC by the radiologist. The “ganglion” or “cyst” that the radiologist identified had to have been in relation to the dorsal scapholunate ligament; if it was not then it did not count as the radiologist identifying the ODGC (in cases where the radiologist commented on a cyst, the location of the cyst was always mentioned relative to another ligament, joint, or bone). After evaluation of the radiologists report, we then reviewed the surgeon's clinic notes to determine whether he or she saw the ODGC on the MRI.

We then personally reviewed the MR images. The typical scan used multiple pulse sequences including T1-weighted and fat saturated proton density weighted coronal (2 mm thickness), gradient recalled echo (GRE) three-dimensional coronal (1 mm thickness), proton density and T2-weighted axial (2 mm thickness), inversion recovery axial (2 mm thickness), and T1-weighted sagittal images (3 mm thickness). We identified the ODGC over the dorsal scapholunate ligament and measured it in three dimensions. In the T2-weighted axial MRI sequence, the medial-to-lateral (M-to-L) and the anterior-to-posterior (A-to-P) lengths were measured ( Fig. 1 ). The proximal-to-distal (P-to-D) length was measured on the T2-weighted sagittal sequence. If T2-weighted sagittal was not available for that study, then the T1-weighted sagittal was used. In all measurements obtained, the largest length in the desired dimension was consistently used. For example, if researchers were looking at M-to-L length, then they measured the ganglion at different sections of the same axial view and recorded the largest measurement. This was performed for all three dimensions in their respective views. We also calculated the volume of the cyst, assuming it was in the shape of a rectangular solid.

Fig. 1.

Example of dorsal occult ganglion cyst arising from the dorsal scapholunate ligament.

Descriptive statistics were used to compare the rate of ODGC identification between radiologists and surgeons and between cases in which “cyst” was written in the MRI requisition form versus those without it. The Mann–Whitney tests were utilized to compare the volume of ODGCs identified and not identified by the radiologists.

Results

After chart review, a total of 28 ODGCs were identified. Of the 28, only 24 individuals had MRIs that passed inclusion/exclusion criteria. There were a total of 25 MRIs because one patient had an ODGC that was seen by the surgeon in the first MRI, but no intervention was performed. About two years later, with recurrent pain, a second MRI was performed. Because our subject population only included patients who underwent surgery for excision of an ODGC, the hand surgeons necessarily identified the ODGC in all 25 MRIs. However, of the 25 MRIs, the radiologist saw and commented on an ODGC in 19, finding 76% of the ODGCs. Fifteen of the 25 MRIs fell into group “1” in which “cyst” was indicated on the requisition form. Thirteen of these 15 (87%) had ODGCs that were identified and reported by the radiologist. Ten of the 25 MRIs fell into group “0” and did not mention cyst in the requisition form. Only 6 of these 10 (60%) had ODGCs that were identified by the radiologist ( Table 1 ).

Table 1. Comparison of dimensions and volumes of all ODGCs.

	Requisition group 1 (cyst mentioned) ( n  = 15)	Requisition group 0 (cyst not mentioned) ( n  = 10)	Total
Radiologist identified cyst	13	6	19
Hand surgeon identified cyst	15	10	25

Abbreviations: ODGC, occult dorsal ganglion cysts.

The dimensions of the ganglion cysts were measured on MRI, and the volume of the cyst was calculated ( Table 2 ). The two-dimensional measurements and the volume of the cysts identified by radiologists were significantly larger than those missed by radiologists ( Table 2 and Fig. 2 ).

Table 2. Comparison of dimensions and volumes of all ODGCs.

	All ODGCs ( n  = 25) mean ± standard deviation (range)	ODGCs identified by radiologists ( n  = 19) mean ± standard deviation (range)	ODGCs missed by radiologists ( n  = 6) mean ± standard deviation (range)	p -Value
M-to-L (cm)	0.81 ± 0.49 (0.2–1.9)	0.94 ± 0.48 (0.3–1.9)	0.4 ± 0.17 (0.2–0.7)	0.011
P–to-D (cm)	0.68 ± 0.37 (0.3–1.6)	0.76 ± 0.38 (0.3–1.6)	0.41 ± 0.19 (0.3–0.8)	0.031
A-to-P (cm)	0.33 ± 0.12 (0.2–0.6)	0.36 ± 0.12 (0.2–0.6)	0.23 ± 0.05 (0.2–0.3)	0.014
Volume (cm 3 )	0.25 ± 0.29 (0.01–1.1)	0.31 ± 0.3 (0.01–1.12)	0.05 ± 0.06 (0.01–0.17)	0.004

Abbreviations: A-to-P, anterior-to-posterior; M-to-L, medial-to-lateral; ODGC, occult dorsal ganglion cysts; P-to-D, proximal-to-distal.

Fig. 2.

The ODGCs identified by radiologists were larger than those they missed. AP, anterior-to-posterior; ML, medial-to-lateral; ODGC, occult dorsal ganglion cysts; PL, proximal-to-distal.

Discussion

This study was a retrospective review of 24 patients who had an ODGC surgically excised and had at least one preoperative wrist MRI. Of the 25 total MRIs, 6 had MRI reports that did not mention the occult dorsal ganglion cyst over the dorsal scapholunate ligament. The radiologists were less likely to identify smaller cysts and were less likely to identify cysts if the MRI requisition form did not mention a cyst as a clinical concern.

The radiologist is tasked with reviewing the entire wrist and all of the incorporated structures (bone, tendon, ligament, nerve, etc.) and thus may either miss or think insignificant the ODGC, especially the smaller ones. However, the hand surgeon has the benefit of correlating a detailed history and exam with the MRI and therefore may be more likely to identify an ODGC (especially the smaller ones) on imaging, as they can focus on a particular sequence and anatomical location. If the surgeon is concerned by an ODGC in a particular location and mentions this in the MRI order form, he or she is more likely to get an MRI report identifying one. However, even if it is mentioned, the radiologist may still miss or not identify the cyst on the report. Indeed, two of the six ODGCs missed in the current study were on MRIs that had “cyst” written in the requisition form. Therefore, the surgeon should review all related imaging of patients since he or she may see pathology that the radiologist did not.

Since undertaking this study, we have had a discussion with the musculoskeletal radiologists and indicated to them that often the most painful wrist cysts are very small. And though we, as hand surgeons, will attempt to more consistently comment on the suspected diagnosis or source of the patient's pain on the requisition form, we recommended to the radiologists that they consistently comment on occult ganglion cysts arising from the dorsal scapholunate ligament.

There are limitations to this study. First, for a radiographic study, the sample size is relatively small. However, it is the largest known MRI study on occult dorsal wrist ganglion cysts. And, although the hand surgeon identified the ODGC in all 25 MRIs, we only studied patients who underwent surgical excision of an ODGC and it is reasonable to assume that the hand surgeon must have identified the ODGC on the MRI before taking the patient to surgery for excision. Thus, a hand surgeon's positive ODGC identification rate on MRI is not truly known, and there may have been patients who were evaluated for dorsal wrist pain and had a “negative MRI” despite actually showing an ODGC. Finally, the shape of the cyst was assumed to be rectangular when calculating cyst volume and therefore is not exact. However, regardless of how the cyst volume was calculated, the conclusion that radiologists miss smaller cysts more often would likely not have changed.

Based on the results of our study, we recommend surgeons write “dorsal scapholunate ligament cyst suspected” on the MRI requisition form when ordering MRIs for patients with suspected ODGCs, and that surgeons personally review and correlate the MRI with the patients history and exam.

Funding Statement

Funding None.