Subsequent DSA Research Articles

Blunt Cerebrovascular Injury: Are We Overscreening Low-Mechanism Trauma?

Screening patients with trauma for blunt cerebrovascular injury with neck CTA is a common practice, but there remains disagreement regarding which patients should be screened. We reviewed adult blunt cerebrovascular injury data from a level 1 trauma center to investigate whether screening is warranted in low-mechanism trauma. We reviewed all neck CTAs performed on adult trauma patients in the emergency department during the 2019 calendar year. Clinical and imaging risk factors for blunt cerebrovascular injury, trauma mechanism, initial neck CTA interpretations, results from subsequent CTA and DSA studies, antiplatelet and anticoagulant treatments, and outcome data were recorded. One thousand one hundred thirty-six neck CTAs met the inclusion criteria, of which 965 (85%) were interpreted as having negative findings; 125, as having indeterminate findings (11%); and 46, as having positive findings (4%). Review of subsequent imaging and clinical documentation led to classification of 40 indeterminate studies (32%) as true-positives and 85 (68%) as false-positives. Blunt cerebrovascular injury was identified in 77 (12.6%) cases meeting and in 9 (1.7%) cases not meeting the expanded Denver criteria. The subset of 204 low-mechanism trauma cases (ground-level falls, blunt assaults, and low-impact motor vehicle collisions) not meeting the expanded Denver criteria (18% of the entire data set) could have been excluded from screening with 1 questionable injury and 0 ischemic strokes missed and 12 false-positive cases prevented. We advocate reservation of blunt cerebrovascular injury screening in low-mechanism trauma for patients meeting the expanded Denver criteria. Further research is needed to determine the behavior of indeterminate cases and to establish criteria for separating true-positive from false-positive findings.

Visualization of the renal artery in kidney transplant patients using time-resolved computed tomography angiography

BackgroundTransplant renal artery stenosis (TRAS) is a post-operative complication which most often occurs between 3 months and 2 years after transplantation. TRAS is associated with kidney failure and hypertension and, thereby, with an increased risk of cardiovascular events.PurposeThe purpose of this retrospective study was to report our experience of perfusion computed tomography angiography (P-CTA) to identify a 50% lumen reduction (as compared to digital subtraction angiography, DSA), assess its subjective image quality and evaluate if contrast-induced acute kidney injury (CI-AKI) occurred.Material and MethodsAll 13 patients who had undergone P-CTA for suspected TRAS at our institution were retrospectively evaluated. At P-CTA, eight or 12 g of iodine were administered intravenously, and five to seven scan sequences were merged into time-resolved images after motion correction. Eight patients underwent subsequent DSA.ResultsThe average patient weight was 76 kg (range 55–97 kg). Image quality was rated as good or excellent for all patients, and pathological changes were shown in 10 of 13 patients undergoing P-CTA. Two patients had a serum creatinine increase of >26 μmol/L during the first 3 days, but serum creatinine was significantly lower in all patients 1 month after P-CTA (165+/−69 μmol/L versus 232+/−66 μmol/L, P < .01). The diagnosis at P-CTA was verified in all eight patients who underwent DSA. However, in two cases with suspected stenosis, renal function was restored without angioplasty.ConclusionAnatomy and blood flow of the transplant renal artery can be visualized using less than a third of the standard contrast media dose by using P-CTA technique.

Donor-Derived Cell-Free DNA Predicts De Novo DSA after Heart Transplantation

PurposeDevelopment of de novo donor-specific HLA antibodies (dnDSA) may contribute to allograft injury and dysfunction, antibody-mediated rejection (ABMR), and potential development of cardiac allograft vasculopathy (CAV). Elevated plasma donor-derived cell-free DNA (dd-cfDNA) levels have been demonstrated during acute cellular rejection (ACR) and ABMR events after heart transplant (HT). The purpose of this study is to investigate the relationship between dd-cfDNA and subsequent DSA development.MethodsFrom the 916 HT patients enrolled in the Surveillance Heart Care Outcome Registry (SHORE), we reviewed 2136 samples of dd-cfDNA surveillance monitoring. Patients with ACR or ABMR on biopsy were excluded from analysis. The dnDSAs included HLA Class I and/or Class II epitopes and were analyzed to development of first dnDSA or last negative test, with censoring at 365 days. There were 613 DSA samples paired with dd-cfDNA levels that were obtained within 30 days of the DSA draw, with prior negative endomyocardial biopsy. Cox proportional hazards model fitting was utilized with dd-cfDNA as a covariate (p<0.05).ResultsFrom analysis of 613 paired samples, 127 (20.7%) demonstrated dnDSA with an associated median dd-cfDNA of 1.20% (IQR: 0.100 - 3.10%). 71 (11.6%) were associated with dnDSA Class I and 93 (15.2%) with Class II. When dichotomized for dd-cfDNA > 0.15%, [FIGURE] the positive likelihood ratio for development of Class I and/or Class II dnDSA (+LR) was 4.47 (p=0.03). When analyzed without censoring at 365 days, using dd-cfDNA at this cutoff, the +LR was 5.68 (p=0.02).ConclusionIn the prospective SHORE cohort, elevated dd-cfDNA levels > 0.15% were associated with increased likelihood for the subsequent development of dnDSA within the first year after heart transplantation. Development of de novo donor-specific HLA antibodies (dnDSA) may contribute to allograft injury and dysfunction, antibody-mediated rejection (ABMR), and potential development of cardiac allograft vasculopathy (CAV). Elevated plasma donor-derived cell-free DNA (dd-cfDNA) levels have been demonstrated during acute cellular rejection (ACR) and ABMR events after heart transplant (HT). The purpose of this study is to investigate the relationship between dd-cfDNA and subsequent DSA development. From the 916 HT patients enrolled in the Surveillance Heart Care Outcome Registry (SHORE), we reviewed 2136 samples of dd-cfDNA surveillance monitoring. Patients with ACR or ABMR on biopsy were excluded from analysis. The dnDSAs included HLA Class I and/or Class II epitopes and were analyzed to development of first dnDSA or last negative test, with censoring at 365 days. There were 613 DSA samples paired with dd-cfDNA levels that were obtained within 30 days of the DSA draw, with prior negative endomyocardial biopsy. Cox proportional hazards model fitting was utilized with dd-cfDNA as a covariate (p<0.05). From analysis of 613 paired samples, 127 (20.7%) demonstrated dnDSA with an associated median dd-cfDNA of 1.20% (IQR: 0.100 - 3.10%). 71 (11.6%) were associated with dnDSA Class I and 93 (15.2%) with Class II. When dichotomized for dd-cfDNA > 0.15%, [FIGURE] the positive likelihood ratio for development of Class I and/or Class II dnDSA (+LR) was 4.47 (p=0.03). When analyzed without censoring at 365 days, using dd-cfDNA at this cutoff, the +LR was 5.68 (p=0.02). In the prospective SHORE cohort, elevated dd-cfDNA levels > 0.15% were associated with increased likelihood for the subsequent development of dnDSA within the first year after heart transplantation.

Value of Contrast-Enhanced MRA versus Time-of-Flight MRA in Acute Ischemic Stroke MRI.

Vessel imaging in acute ischemic stroke is essential to select patients with large-vessel occlusion for mechanical thrombectomy. Our aim was to compare the diagnostic accuracy of time-of-flight MR angiography and contrast-enhanced MR angiography for identification of vessel occlusion and collateral status in acute ischemic stroke. One hundred twenty-three patients with stroke with large-vessel occlusion before thrombectomy were included in this retrospective study. Before thrombectomy, 3T MR imaging, including conventional 3D TOF-MRA of the intracranial arteries and contrast-enhanced MRA of intra- and extracranial arteries, was performed. Both techniques were assessed independently by 2 neuroradiologists for location of the occlusion, imaging quality, and collateral status. Findings were compared, with subsequent DSA as the reference standard. Both techniques had good interrater agreement of κ = 0.74 (95% CI, 0.66-0.83) for TOF-MRA and κ = 0.72 (95% CI, 0.63-0.80) for contrast-enhanced MRA. Occlusion localization differed significantly on TOF-MRA compared with DSA (P < .001), while no significant difference was observed between DSA and contrast-enhanced MRA (P = .75). Assessment of collaterals showed very good agreement between contrast-enhanced MRA and DSA (94.9% with P = .25), but only fair agreement between TOF-MRA and DSA (23.2% with P < .001). Contrast-enhanced MRA offers better diagnostic accuracy than TOF-MRA in acute ischemic stroke. Contrast-enhanced MRA was superior in localizing vessel occlusion within a shorter acquisition time while providing a larger coverage, including extracranial vessels, and a more accurate assessment of collateral status. These results support inclusion of contrast-enhanced MRA in acute stroke MR imaging, perhaps making TOF-MRA superfluous.

Neurosurgery (Neuro Interventional)

Purpose: CTA is becoming the frontline modality to reveal aneurysms in patients with SAH. However, in about 20% of SAH patients no aneurysm is found. In these cases, intra-arterial DSA is still performed. Our aim was to evaluate whether negative findings on CTA can reliably exclude aneurysms in patients with acute SAH. Materials and Method: We conducted a retrospective analysis of all DSA performed from August 2010 to July 2014 in patients with various indications. We selected patient who presented with SAH and had a negative CTA. Findings of the CTA were compared with DSA. Results: 857 DSA were performed during the study period. 51(5.95%) patients with SAH and negative findings on CTA who underwent subsequent DSA were identified. Of these, only 3(5.9%) of patients had positive findings on the DSA. One patient had a posterior inferior cerebellar artery aneurysm on the DSA, not seen on CTA due to the incomplete coverage of the head. Second patient’ CTA did not show any evidence of aneurysm. DSA showed suspicious dissection of the right vertebral artery, potentially iatrogenic. The third patient’s DSA showed suspicious tiny protuberance from left ICA, possibly infundibulum. Conclusion: In patients with SAH, negative CTA findings are reliable in ruling out aneurysms in any pattern of SAH on CT.

Correlation between CTA and subsequent DSA collateral scores in acute ischemic stroke (P6.015)

Correlation between CTA and subsequent DSA collateral scores in acute ischemic stroke (P6.015)

Hyperintense basilar artery on FLAIR MR imaging: diagnostic accuracy and clinical impact in patients with acute brain stem stroke.

FLAIR-hyperintense vessels are known to be a sign of sluggish collateral blood flow in hemispheric vessel occlusion. Additionally, they seem to have a prognostic implication. The aim of the current study was to evaluate the hyperintense configuration of the basilar artery (FLAIR-hyperintense basilar artery) as a marker of basilar artery occlusion and as a predictor of patient outcome. We retrospectively identified 20 patients with basilar artery occlusion who initially underwent MR imaging with subsequent DSA. The diagnostic accuracy of the FLAIR-hyperintense basilar artery sign was tested by 4 independent readers in a case-control design, and the relation among FLAIR-hyperintense basilar artery and DWI posterior circulation-ASPECTS, patient outcome, and patient survival was evaluated. To grade the extent of the FLAIR-hyperintense basilar artery sign, we generated a score by counting the number of sections from the basilar tip to the foramen magnum in which a hyperintense signal in the vessel lumen was present multiplied by the section thickness. The FLAIR-hyperintense basilar artery sign showed moderate sensitivity (65%-95%) but very good specificity (95%-100%) and accuracy (85%-93%) for the detection of basilar artery occlusion. Substantial or excellent inter-reader agreement was observed (Cohen κ, 0.64-0.85). The FLAIR-hyperintense basilar artery inversely correlated with the posterior circulation-ASPECTS (r = -0.67, P = .01). Higher FLAIR-hyperintense basilar artery scores were associated with patient death (28.3 ± 13.7 versus 13.4 ± 11.1, P < .05). The FLAIR-hyperintense basilar artery sign proved to be a valuable marker of vessel occlusion and may substantially support the diagnosis of basilar artery occlusion. The established FLAIR-hyperintense basilar artery score may be helpful for the prediction of individual patient survival.

1:54 PM, Abstract No. 111 - Provocative mesenteric angiography for gastrointestinal hemorrhage

Mesenteric angiography with transcatheter embolization can be a highly effective means of controlling gastrointestinal bleeding (GIB) when a source of hemorrhage is identified. However, given the intermittent nature of hemorrhage, a majority of cases of mesenteric angiography performed for GIB fail to demonstrate active bleeding. One approach for increasing the positive diagnostic rate is that of provocative angiography. Here we report our recent experience and outcomes with this protocol. A protocol for provocative angiography at a major academic medical center was developed and standardized as follows. In all cases at least one prior negative mesenteric arteriogram without provocation has been performed, any contraindications to the thrombolytic agent, tissue plasminogen activator (tPA), are excluded and surgical backup is obtained. The superior mesenteric artery is selectively catheterized and injected with 5000 units of heparin and 100 micrograms of nitroglycerin. Subsequent DSA is performed. If no source of hemorrhage is identified, 10 mg of tPA are administered via the catheter and repeat angiography is performed. If negative, the inferior mesenteric artery is catheterized and an additional 10 mg of tPA are administered. The total dose of tPA is limited to 20 mg. 19 cases of provocative mesenteric angiography were performed from June 2008 through September 2013. Of these, 14 (74%) were negative despite the provocative maneuvers. 5/19 (26%) demonstrated active contrast extravasation. Of these positive cases, 3 (60%) were successfully embolized at the time of angiography. In one case, the decision was made in conjunction with the surgical staff to defer embolization in favor of surgery. In the second case, a very small focus of bleeding was identified in distal arterial branches which could not be safely accessed. Provocative angiography can be performed safely, without causing life-threatening hemorrhage. By provoking hemorrhage in a controlled environment, positive rates are increased and the majority of these patients can be treated immediately. This can reduce the number of cases requiring invasive surgery.

Recurrent inflammatory stenosis of the M1 segment: diagnostic and therapeutic considerations

Dear Sir: Recent advances of imaging technology have helped to identify stenoses of intracranial arteries as an important cause of cerebral ischemia [1]. It has been estimated that up to 10% of strokes are caused by intracranial occlusive disease. The introduction of intracranial angioplasty and stenting has added a new therapeutic option [2]. However the management of patients with a progressive middle cerebral artery stenosis can remain difficult even with a combination of medical and interventional treatment. A 60-year-old female patient of Indian origin presented in August 2008 with subarachnoid haemorrhage centred on the right Sylvian fissure. CT angiography revealed a tight stenosis of the proximal right middle cerebral artery (M1segment) as the sole abnormality. Subsequent intra-arterial DSA confirmed the presence of the stenosis and also showed distended lenticulostriate arteries on the right and an expansion in the extent of brain tissue supplied from the left ICA at the expense of the right MCA territory. The rupture of one of the friable collateral blood vessels was presumed to be the cause for the subarachnoid haemorrhage, rendering the stenosis symptomatic. As the patient had a history of coronary artery disease and hypercholesterolaemia, the stenosis was initially considered to be due to atherosclerosis. However, the patient subsequently developed transient episodes of left arm weakness and possible jaw claudication. MRI brain did not show any ischaemic lesions, but MRA showed new stenoses affecting the proximal left MCA and distal right internal carotid artery. Contrast-enhanced MRI demonstrated contrast enhancement in the wall of the right MCA. The combination of vessel wall enhancement and newly developed stenoses suggested cerebral vasculitis. Extensive investigation for a systemic vasculitis and CSF tests failed to show any abnormalities. Based on the imaging appearances and the patient’s recurrent symptoms, she was treated with steroids and cyclophosphamide, while her treatment for atheromatous disease was continued. The patient’s symptoms persisted after an initial course of high dose steroids, and a repeat MRA showed worsening of the MCA stenosis. Therefore an angioplasty of the M1 stenosis was performed under general anaesthesia 3 months (end of October 2008) after initial admission (Fig. 1a, b). The balloon (Gateway 2×8 mm) was inflated three times resulting in a significant improvement of the right hemispheric perfusion. There were no procedural complications, either clinically or on DWI MRI. After immunosuppressive treatment with cyclophosphamide for 6 months, a contrast-enhanced MRI showed improvement, though not a complete resolution of the vessel wall enhancement (Fig. 1c). The left middle cerebral artery stenosis had resolved. This improvement was regarded as supporting the presumed diagnosis of vasculitis with response to treatment. W. Kuker (*) : J. Downer Department of Neuroradiology, West Wing John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK e-mail: wilhelm.kuker@clneuro.ox.ac.uk

Asymptomatic arteriovenous malformation recurrence in an adult

Dear Editor,Consensus exists that angiographically confirmed completeresection of cerebral arteriovenous malformations (AVM)can be regarded as the definite treatment. Only a fewreports of AVM recurrences—mostly in children—areavailable so far [8, 9, 13, 14]. AVM recurrence in adultsseems to be extremely rare, with only five case reportsexisting to date [1, 3, 4, 6, 11]. We present the first reportedcase of asymptomatic AVM recurrence in an adult.In June 2008, a 30-year-old female suffered a spontane-ous intracerebral hematoma in the left parietal lobeinvolving the corpus callosum and the cingulate gyrus,leading to acute headaches, vomiting, coordination disorder,and right-sided hemihypaesthesia. The haemorrhage wasinduced by a small AVM in the left parietal lobe (Fig. 1a).Surgery was performed 1 month after the bleeding withoutprevious embolization. Angiography (DSA) on postopera-tive day 6 confirmed the complete removal of the AVM(Fig. 1b). Postoperatively, the patient was able to return toall activities of daily life, including work, without perma-nent impairment. In November 2010, MRI performedbecause of chronically persistent headaches revealed anew vascular convolute at the dorsolateral resection margin(Fig. 1c, d) confirmed by a subsequent DSA as an AVMrecurrence (Fig. 1e, f). The patient underwent a secondsurgery, again with angiographically verified completeAVM resection (Fig. 1g).Our case confirms that even adults are at risk for AVMrecurrence despite initial inconspicuous postoperative angio-graphic control. In the previously reported cases, AVMrecurrence was accompanied by haemorrhagic events orseizures [1, 3, 4, 6, 11]. Codd et al. even described a doublerecurrence. In this case the second recurrence was detectedon a routine DSA indicated because of the first one [1]. Inour patient the recurrent AVM was detected by MRI carriedout because of chronically persistent headaches with no otherspecific symptoms.Among the described recurrent cases in adults [1, 3, 4, 6,11], includingourcase,AVMswerelocalizedbothineloquentand non-eloquent regions, with both deep and superficialvenous drainage, respectively, rendering these parametersobviously not relevant for recurrence. Time to recurrenceranged between 10 months and 9 years. Patient age rangedbetween 17 and 33 years at the time of the initial surgery, andbetween 21 and 40 years at the detection of the recurrence.Remarkably, all of them were small in size (<3 cm).Various possible mechanisms of AVM recurrence arediscussed in the literature. One explanation is an incompleteresection disguised by vasospasm or thrombosis withinresidual AVM compartments [6]. The second theoryassumes genetically predisposed abnormal angiogenesismediated by increased vascular endothelial growth factor(VEGF) [12] or cellular signalling proteins pERK (phos-phorylated extracellular signal–regulated kinase) andCD105 (endoglin), respectively [13]. The third possibleexplanation is a “hidden compartment” [10]: AVMs, beingmulticompartmental, may comprise a “reserve nidus”,which remains angiographically hidden because of verylow or absent blood flow in its vessels as a result of internalsteel as long as “active compartments” seen on angiogramare not resected.Regardless of the pathological mechanism, AVM recur-rences remain a rare but potentially serious sequel aftercomplete surgical obliteration. The actual rate of recurrence

Segmental cerebral vasoconstriction: Successful treatment of secondary cerebral ischaemia with intravenous prostacyclin

We describe a 23-year-old male patient who presented with spontaneous intermittent and increasing attacks of severe, left-sided thunderclap headache combined with rapidly progressive muscle weakness and dysphasia, including gradual loss of consciousness. Subsequent CT, MRI and DSA showed progressive brain ischaemia and oedema within the left cerebral hemisphere with strict ipsilateral segmental arterial vasoconstriction. Despite extensive medical care, including steroids, the patient deteriorated rapidly. However, the clinical course changed dramatically within 15 h after the start of an intravenous infusion of prostacyclin at a dose of 0.9 ng/kg/min, with an almost complete recovery of consciousness and speech. In addition the pathophysiological alterations seen on magnetic resonance (imaging and digital) subtraction angiography including diffusion-weighted imaging and apparent diffusion coefficient maps shortly before prostacyclin treatment were clearly reduced when the patient was examined 3-4 days later and he continued to recover thereafter. Although not fully compatible, our case had several clinical characteristics and radiological findings reminiscent of those of the 'segmental reversible vasoconstriction syndrome', sometimes called the Call-Fleming syndrome.

Negative CT Angiography Findings in Patients with Spontaneous Subarachnoid Hemorrhage: When Is Digital Subtraction Angiography Still Needed?

CTA is becoming the frontline modality to reveal aneurysms in patients with SAH. However, in about 20% of SAH patients no aneurysm is found. In these cases, intra-arterial DSA is still performed. Our aim was to evaluate whether negative findings on CTA can reliably exclude aneurysms in patients with acute SAH. We conducted a retrospective analysis of all negative findings on CTAs performed from 2005 to 2009 in patients with spontaneous SAH. Findings were compared with DSA. CTAs were performed with a 64-section multidetector row CT scanner. One hundred ninety-three patients with SAH and negative findings on CTA who underwent subsequent DSA were identified. The distribution of blood on unenhanced CT was the following: PMH in 93 patients, diffuse aneurysmal pattern in 50, no blood on CT (xanthochromic LP) in 32, and peripheral sulcal distribution in 18. All patients with PMH had negative findings on DSA. One patient with no blood on CT had vasculitis on DSA. Six of 18 (33%) patients with peripheral blood had vasculitis on DSA. Three of these were also diagnosed by CTA. All except 1 patient with diffuse aneurysmal blood had negative findings on DSA. One patient was diagnosed with an aneurysm on DSA (1/50, 0.5%). Repeat delayed DSA performed in 28 of these patients revealed a small aneurysm in 4 (14%). Five patients had a complication of DSA (2.6%); 1 was a clinical stroke (0.5%). In patients with SAH, negative CTA findings are reliable in ruling out aneurysms in the PMH pattern or no blood on CT. DSA is indicated in the diffuse aneurysmal pattern of SAH, and repeat delayed DSA is required if the initial DSA findings are negative. When the blood is peripheral, CTA should be scrutinized for vasculitis and DSA is recommended for confirmation.

Verbesserte Lokalisationsdiagnostik der spinalen duralen AV-Fistel durch die CE-MRA bei 3 T

The standard for the detection and localization of spinal dural and perimedullary AV fistulas has been digital subtraction angiography. The purpose of this study was to correctly locate dural AV fistulas using high-resolution (hr), contrast-enhanced (ce) MRA at 3 T or at least to estimate the site within a range of two to three segments. As a result, the radiation exposure, contrast dose and risk of complications were able to be reduced. Five patients with typical clinical symptoms and the characteristic signs in spinal MRI were examined at 3 T (GE Signa Excite HD). Hr, ce MR angiography and a time-resolved sequence (TRICKS) were compared and correlated with the subsequent DSA and the operation record with respect to the site of the fistula. In addition, the amount of contrast agent and the number of selectively catheterized segmental arteries in DSA were analyzed. In all patients, a dural AV fistula was able to be demonstrated by hr, ce MRA, and the side and the segmental level of the point of the fistula were correctly predicted and confirmed in subsequent DSA as well as in the operation record. In time-resolved MRA the determined location was correct in one of the five cases. In the remaining 4 cases no definitive mapping was possible. In hr, ce MRA at 3 T the localization of the point of the fistula in a spinal AVF is highly reliable so that the radiation time and the amount of contrast medium can be reduced. Hr, ce MRA is superior to the time-resolved sequence (TRICKS).

Disappearance and reappearance of a cerebral aneurysm: a case report

The false-negative rate of DSA in the setting of a ruptured cerebral aneurysm is approximately 15% (Topcuoglu M, Ogilvy C, Carter B, et al. Subarachnoid hemorrhage without evident cause on initial angiography studies: diagnostic yield of subsequent angiography and other neuroimaging tests. J Neurosurg 2003;98:1235-1240). Detecting these aneurysms is imperative to avoid repeat hemorrhage. Rarely, one is able to document the phenomenon of the disappearance and subsequent reappearance of the ruptured aneurysm. This is a case report of subarachnoid hemorrhage (SAH) in which a cerebral aneurysm of the M1 segment of the left proximal middle cerebral artery was initially detected by CTA at an outside hospital only to evade detection with both CTA and DSA at our institution. Repeat DSA 1 week later revealed the culprit aneurysm, which was then treated endovascularly. Patients with significant SAH and negative DSA findings should be considered for further diagnostic testing including CTA or repeat DSA. The current literature supports the strategy used at our institution of initial CTA and DSA in the setting of SAH, and then subsequent repeat DSA as warranted if the initial studies are nondiagnostic. Timing of repeat examination, as demonstrated in this case, should favor a shorter time course.