Centripetal Propagation of Vasoconstriction at the Time of Headache Resolution in Patients with Reversible Cerebral Vasoconstriction Syndrome

Headache Attributed to Reversible Cerebral Vasoconstriction Syndrome (RCVS)

Reversible cerebral vasoconstriction syndrome (RCVS) is a condition with variable outcomes presenting a new onset thunderclap headache accompanied by focal neurological symptoms or seizures. It can be idiopathic or arise secondarily to a variety of trigger factors. The condition is increasingly recognized in clinical practice, but many facets remain poorly understood. This article aims to clarify the headache characteristics in RCVS, the temporal association of angiographic findings, the potential association of the condition with SARS-CoV-2 infection, and the clinical presentation of RCVS in children and is based on a systematic PRISMA search for published analytical or large descriptive observational studies. Data from 60 studies that fulfilled specific criteria were reviewed. Most people with RCVS exhibit a typical thunderclap, explosive, or pulsatile/throbbing headache, or a similar acute and severe headache that takes longer than 1 min to peak. Atypical presentations or absence of headaches are also reported and may be an underrecognized phenotype. In many cases, headaches may persist after resolution of RCVS. Focal deficits or seizures are attributed to associated complications including transient ischemic attacks, posterior reversible encephalopathy syndrome, ischemic stroke, cerebral edema, and intracranial hemorrhage. The peak of vasoconstriction occurs usually within two weeks after clinical onset, possibly following a pattern of centripetal propagation, and tends to resolve completely within 3 months, well after symptoms have subsided. There are a few reports of RCVS occurring in relation to SARS-CoV-2 infection, but potential underlying pathophysiologic mechanisms and etiological associations have not been confirmed. RCVS occurs in children most often in the context of an underlying disease. Overall, the available data in the literature are scattered, and large-scale prospective studies and international collaborations are needed to further characterize the clinical presentation of RCVS.

Update on primary headache associated with sexual activity and primary thunderclap headache

BACKGROUND

This narrative review aims to provide an update on primary headache associated with sexual activity and primary thunderclap headache.

METHODS

We conducted a literature search on PubMed with the keywords "headache associated with sexual activity", "sexual headache", "orgasmic cephalalgia", and "coital cephalalgia" in addition to "thunderclap headache" to assess the appropriateness of all published articles in this review.

RESULTS

Primary headache associated with sexual activity is a "primary" headache precipitated by sexual activity, which occurs as sexual excitement increases (progressive at onset), or manifests as an abrupt and intense headache upon orgasm (thunderclap at onset) or combines these above two features. Primary headache associated with sexual activity is diagnosed after a thorough investigation, including appropriate neuroimaging studies, to exclude life-threatening secondary causes such as subarachnoid hemorrhage. According to the criteria of the third edition of the International Classification of Headache Disorders, primary thunderclap headache is also a diagnosis by exclusion. The pathophysiology of primary headache associated with sexual activity and primary thunderclap headache remains incompletely understood. Treatment may not be necessary for all patients since some patients with primary headache associated with sexual activity and primary thunderclap headache have a self-limiting course.

CONCLUSION

A comprehensive neuroimaging study is needed for distinguishing primary headache associated with sexual activity or primary thunderclap headache from secondary causes. Primary headache associated with sexual activity and primary thunderclap headache are self-limited diseases and the prognoses are good, but some patients with primary headache associated with sexual activity may have a prolonged course.

Reversible Cerebral Vasoconstriction Syndrome Patients with a History of Migraine: A Retrospective Case-control Study

Objective We investigated the clinical characteristics of patients with reversible cerebral vasoconstrictor syndrome who had a history of migraine before the onset and considered the relationship between these two pathologies. Methods We investigated 98 patients who underwent magnetic resonance angiography within 14 days of the onset of reversible cerebral vasoconstriction syndrome at our hospital. Of these, 11 cases involved recurrences, so data from 87 patients were analyzed. Materials All consecutive patients diagnosed with reversible cerebral vasoconstrictor syndrome at our institution between October 2010 and July 2021. Results Fifty of the 87 patients (57%) had a history of migraine. A multivariate analysis revealed that the following clinical factors were significantly more frequent in patients with a history of migraine than in those without such a history: female sex; emotional situations as a trigger of the onset; presence of deep and subcortical white matter hyperintensity, absence of vasoconstriction in the M1 portion of the middle cerebral artery, and absence of other cerebral lesions on initial magnetic resonance imaging; absence of vasoconstriction of the basilar artery on follow-up magnetic resonance imaging; and progression of deep and subcortical white matter hyperintensity in the chronic stage. Conclusion Reversible cerebral vasoconstrictor syndrome patients with a history of migraine showed clinical features of migraine, including one aspect of cerebral small-vessel disease due to endothelial dysfunction, as a common causative condition.

Persistent brain damage in reversible cerebral vasoconstriction syndrome on 99mTc-ethyl cysteinate dimer single-photon emission computed tomography: A long-term observational study

BACKGROUND

Blood-brain barrier (BBB) breakdown is considered a key step in the pathophysiology of reversible cerebral vasoconstriction syndrome (RCVS); however, its temporal course remains unclear. Based on the characteristics and dynamics of ^99mTc-ethyl cysteinate dimer (^99mTc-ECD) as a tracer, ^99mTc-ECD single-photon emission computed tomography (SPECT) can detect not only hypoperfusion but also BBB breakdown and/or brain tissue damage. Therefore, this study aimed to investigate this course using ^99mTc-ECD SPECT.

METHODS

Between 2011 and 2019, we enrolled seven patients (one male and six female patients) with RCVS without ischemic or hemorrhagic stroke or posterior reversible encephalopathy syndrome. ^99mTc-ECD SPECT was performed repeatedly in each patient. SPECT data were statistically analyzed using an easy Z-score imaging system.

RESULTS

Thunderclap headache was the initial symptom in all the patients and was most commonly triggered by bathing (three patients). All the patients exhibited vasoconstriction and reduced cerebral uptake of ^99mTc-ECD during the acute stage. Follow-up assessment from 3 to 16 months showed that reduced cerebral uptake persisted in all the patients, even after the vasoconstriction had resolved.

CONCLUSION

Reduced cerebral uptake of ^99mTc-ECD persisted in the late stage of RCVS, even after vasoconstriction and headache subsided. BBB breakdown and/or brain tissue damage may underlie this phenomenon. ^99mTc-ECD SPECT is an effective neuroimaging method to detect brain functional abnormalities, reflecting BBB breakdown or tissue damages, throughout the treatment course of RCVS.

[Subdural hematoma with reversible cerebral vasoconstriction syndrome: a case report]

A 71-year-old man had persistent cervical pain secondary to thunderclap headache during sleep. MRI conducted the next morning revealed subdural hematoma and convexity subdural hemorrhage on the right occipital region, and the patient was hospitalized. MRA showed vascular narrowing in the bilateral PCA. Follow-up MRA on day 8 of admission showed aggravated vascular narrowing of PCA, indicative of reversible cerebral vasoconstriction syndrome (RCVS). The patient was treated with a calcium-channel antagonist. Post-discharge MRA showed improvement of PCA narrowing, and the diagnosis of RCVS was confirmed.

Pathophysiology of reversible cerebral vasoconstriction syndrome

Reversible cerebral vasoconstriction syndrome (RCVS) is a complex neurovascular disorder being recognized during the past two decades. It is characterized by multiple abrupt severe headaches and widespread cerebral vasoconstrictions, with potential complications such as ischemic stroke, convexity subarachnoid hemorrhage, intracerebral hemorrhage and posterior reversible encephalopathy syndrome. The clinical features, imaging findings, and dynamic disease course have been delineated. However, the pathophysiology of RCVS remains elusive. Recent studies have had substantial progress in elucidating its pathogenesis. It is now believed that dysfunction of cerebral vascular tone and impairment of blood–brain barrier may play key roles in the pathophysiology of RCVS, which explains some of the clinical and radiological manifestations of RCVS. Some other potentially important elements include genetic predisposition, sympathetic overactivity, endothelial dysfunction, and oxidative stress, although the detailed molecular mechanisms are yet to be identified. In this review, we will summarize what have been revealed in the literature and elaborate how these factors could contribute to the pathophysiology of RCVS.

Hyperintense posterior cerebral artery sign in patients with reversible cerebral vasoconstriction syndrome

Background:

This study investigated hyperintense vessel signs (HVS) on fluid-attenuated inversion recovery imaging in the P1–2 portions of posterior cerebral arteries (PCAs) as a “hyperintense PCA sign” and HVS of cortical arteries. We retrospectively examined whether these signs would be useful in diagnosing reversible cerebral vasoconstriction syndrome (RCVS) in the acute phase.

Methods:

Eighty patients with RCVS who underwent initial magnetic resonance imaging (MRI) within 7 days of onset were included in this study. HVS and related clinical factors were examined.

Results:

On initial MRI of RCVS patients, hyperintense PCA sign and HVS of cortical arteries were seen in 21 cases (26%) and 38 cases (48%), respectively. In patients showing hyperintense PCA sign, vasoconstriction of the A2–3 portion was a significant clinical factor. Conversely, vasoconstriction of the M1 and P1 portions and the presence of white matter hyperintensity on initial and chronic-stage MRI were significantly associated with the presence of HVS in cortical arteries.

Conclusion:

Because rich collateral flow exists around PCAs, the frequency of hyperintense PCA sign is not high. However, hyperintense PCA sign findings in patients with suspected RCVS offer credible evidence of extreme flow decreases due to vasoconstriction in peripheral PCAs and other arteries associated with the collateral circulation of PCAs. Conversely, HVS in cortical arteries tend to reflect slow antegrade circulation due to vasoconstriction of peripheral vessel and major trunks. Both signs appear useful for auxiliary diagnosis of acute-phase RCVS.

Distribution of symptomatic cerebral vasospasm following subarachnoid hemorrhage assessed using cone-beam CT angiography

BACKGROUND AND PURPOSE

Cone-beam CT angiography (CB-CTA) provides a three-dimensional spatial resolution which is, so far, unmatched in clinical practice compared with other conventional techniques such as two-dimensional digital subtracted angiography. We aimed to assess the distribution of symptomatic cerebral vasospasm following aneurysmal subarachnoid hemorrhage (aSAH) using CB-CTA.

METHODS

30 consecutive patients with aSAH undergoing vasospasm percutaneous balloon angioplasty (PBA) were recruited and underwent CB-CTA in this single-center prospective cohort series. Intracranial arteries were systematically analyzed by two independent observers from the large trunks to the distal cortical branches and perforators using a high-resolution reconstruction protocol. Intermediate and severe cerebral vasospasm was defined as 30-50% and >50% narrowing in the diameter of the vessel, respectively.

RESULTS

35 arterial cervical artery territories were analyzed, of which 80% were associated with clinical or radiological signs of delayed cerebral ischemia. The median spatial resolution was 150 µm (range 100-250 µm). Intermediate or severe vasospasm was observed in the proximal (86%, 95% CI 74% to 97%), middle (89%, 95% CI 78% to 99%), and distal (60%, 95% CI 44% to 76%) segments of the large trunks, as well as the cortical branches (11%, 95% CI 1% to 22%). No vasospasm was observed in basal ganglia or cortical perforators, or in arteries smaller than 900 µm. Vasospasm was more severe in middle or distal segments compared with proximal segments in 43% (95% CI 26% to 59%) of cases.

CONCLUSIONS

Our study demonstrated that symptomatic cerebral vasospasm following aSAH did not involve arteries smaller than 900 µm, and frequently predominated in middle or distal segments. These results offer new insights into the potential management options for vasospasm using PBA.

Diagnosis and classification of headache associated with sexual activity using a composite algorithm: A cohort study

BACKGROUND

To differentiate primary headache associated with sexual activity from other devastating secondary causes.

METHODS

In this prospective cohort, we recruited consecutive patients with at least 2 attacks of headache associated with sexual activity from the headache clinics or emergency department of a national medical center from 2005 to 2020. Detailed interview, neurological examination, and serial thorough neuroimaging including brain magnetic resonance imaging and magnetic resonance angiography scans were performed on registration and during follow-ups. Patients were categorized into four groups, i.e. primary headache associated with sexual activity, reversible cerebral vasoconstriction syndrome, probable reversible cerebral vasoconstriction syndrome, and other secondary headache associated with sexual activity through a composite clinic-radiological diagnostic algorithm. We compared the clinical profiles among these groups, including sex, age of onset, duration, quality, and clinical course ("chronic" indicates disease course ≥ 1 year). In addition, we also calculated the score of the reversible cerebral vasoconstriction syndrome₂, a scale developed to differentiate reversible cerebral vasoconstriction syndrome from other intracranial vascular disorders.

RESULTS

Overall, 245 patients with headache associated with sexual activity were enrolled. Our clinic-radiologic composite algorithm diagnosed and classified all patients into four groups, including 38 (15.5%) with primary headache associated with sexual activity, 174 (71.0%) with reversible cerebral vasoconstriction syndrome, 26 (10.6%) with probable reversible cerebral vasoconstriction syndrome, and 7 (2.9%) with other secondary causes (aneurysmal subarachnoid hemorrhage (n = 4), right internal carotid artery dissection (n = 1), Moyamoya disease (n = 1), and meningioma with hemorrhage (n = 1)). These four groups shared similar clinical profiles, except 26% of the patients with primary headache associated with sexual activity had a 3 times greater chance of running a chronic course (≥ 1 year) than patients with reversible cerebral vasoconstriction syndrome. Of note, the reversible cerebral vasoconstriction syndrome₂ score could not differentiate reversible cerebral vasoconstriction syndrome from other groups.

CONCLUSION

Our composite clinic-radiological diagnostic algorithm successfully classified repeated headaches associated with sexual activity, which were predominantly secondary and related to vascular disorders, and predicted the prognosis. Primary headache associated with sexual activity and reversible cerebral vasoconstriction syndrome presented with repeated attacks of headache associated with sexual activity may be of the same disease spectrum.

Quantitative arterial spin labeling magnetic resonance imaging analysis of reversible cerebral vasoconstriction syndrome: A case series

OBJECTIVE

This study aimed to quantify chronological cerebral blood flow (CBF) changes using arterial spin labeling (ASL) magnetic resonance imaging in patients with reversible cerebral vasoconstriction syndrome (RCVS).

BACKGROUND

Quantitative ASL analyses in RCVS have not been well described in the literature.

METHODS

Quantification of ASL using an automated region-of-interest placement software and a 5-point visual scale of vasoconstriction severity was performed in five RCVS patients. The association between CBF changes and RCVS-related complications was evaluated.

RESULTS

Quantitative ASL revealed variable patterns of decreasing CBF in the first week, followed by subsequent increases. Notably, arterial vasoconstriction paradoxically progressed despite an increase in CBF from the first to the second week; this increase was relatively higher in patients with both cortical subarachnoid hemorrhage and posterior reversible encephalopathy syndrome.

CONCLUSIONS

Quantitative ASL revealed that CBF initially decreased and subsequently increased, especially in the second week. These changes may serve as surrogate imaging markers for RCVS-related complications, and could further contribute to understanding the pathology of RCVS.

Reversible cerebral vasoconstriction syndrome: the importance of follow-up imaging within 2 weeks

Aim

In patients with thunderclap headaches, reversible cerebral vasoconstriction syndrome (RCVS) should be considered as a differential diagnosis. However, RCVS diagnosis in the emergency department (ED) remains challenging. This report describes the clinical features and factors related to RCVS diagnosis and suggests diagnostic strategies for its management.

Methods

We retrospectively reviewed the medical records of eight patients diagnosed with RCVS from January 2010 to March 2019 (aged 18–69 years, 5 women).

Results

The median duration from the ED visit to RCVS diagnosis was 6 days (range, 1–11 days). Of the eight patients, seven were middle‐aged, six had apparent triggers, six had subarachnoid hemorrhage (SAH), five had high systolic blood pressure, and none had any specific abnormality observed upon physical examination. At the initial visit, RCVS was diagnosed in only one patient who had a history of RCVS. Of the other patients, SAH was diagnosed in two, and primary headache was diagnosed in four patients with negative computed tomography (CT) findings. Based on follow‐up angiography (e.g., magnetic resonance angiography), seven of eight patients with convexal SAH were diagnosed with RCVS (as the cause of SAH).

Conclusion

Reversible cerebral vasoconstriction syndrome with negative CT findings at the ED visit was likely to be misdiagnosed as a primary headache. In patients with thunderclap headache and negative CT findings, physicians should consider RCVS as a differential diagnosis, inform patients of the risk of RCVS, and undertake follow‐up imaging within 2 weeks.

Temporal Profile of Blood-Brain Barrier Breakdown in Reversible Cerebral Vasoconstriction Syndrome

Background and Purpose- Reversible cerebral vasoconstriction syndrome (RCVS) has a unique temporal course of vasoconstriction. Blood-brain barrier (BBB) breakdown is part of the pathophysiology of RCVS, but its temporal course is unknown. We aimed to investigate the temporal profile of BBB breakdown and relevant clinical profiles in a large sample size. Methods- In this prospective observatory bicenter study, patients who underwent contrast-enhanced fluid-attenuated inversion recovery magnetic resonance imaging within 2 months from onset were included. The presence and extent of BBB breakdown were evaluated using contrast-enhanced fluid-attenuated inversion recovery magnetic resonance imaging. Contrast-enhanced fluid-attenuated inversion recovery magnetic resonance imaging data were analyzed using a semiautomated segmentation technique to quantitatively measure the area of Gadolinium leakage into cerebrospinal fluid space. The univariable and multivariable linear regressions were performed to investigate the independent effect of time from onset with adjustment for other covariates. Results- In the 186 patients with angiogram-proven RCVS included in this analysis, BBB breakdown was observed in 52.6%, 56.8%, 30.3%, 40.0%, and 23.8% in the first, second, third, fourth, and ≥fifth week after onset. The extent of BBB breakdown peaked at first and second week, whereas the peak of vasoconstriction was observed at the third week after onset. Multivariable analysis showed the second week from onset (β, 3.35 [95% CI, 0.07-6.64]; P=0.046) and blood pressure surge (β, 3.84 [95% CI, 1.75-5.92]; P<0.001) were independently associated with a greater extent of BBB breakdown. A synergistic effect of time from onset and blood pressure surge was found (P for interaction=0.006). Conclusions- Frequency and extent of BBB breakdown are more prominent during the early stage in patients with RCVS, with an earlier peak than that of vasoconstriction. The temporal course of BBB breakdown may provide a pathophysiologic background of the temporal course of neurological complications of RCVS.

Effect of Nimodipine Treatment on the Clinical Course of Reversible Cerebral Vasoconstriction Syndrome

Background: In reversible cerebral vasoconstriction syndrome (RCVS), nimodipine is currently used for the treatment, although no evidence is available to support its disease-modifying effect. In this prospective observational study, we investigated whether earlier nimodipine treatment can modify the clinical course of reversible cerebral vasoconstriction syndrome.

Methods: We prospectively observed patients with angiogram-proven RCVS within 1 month after onset in the Samsung Medical Center between October 2015 and January 2018. Nimodipine was started in all patients immediately after diagnosis. Time from onset to the first nimodipine treatment was categorized as tertiles. We analyzed Kaplan-Meier curve and Cox proportional hazard model to test if the timing of nimodipine treatment can affect the clinical course of thunderclap headaches (TCHs) defined as the duration from onset to remission of thunderclap headaches.

Results: In 82 patients included in this study, 71 (86.6%) patients showed remission of TCHs after starting nimodipine treatment. When categorized into earliest (<6 days), early (6–13 days), and late (≥14 days) treatment groups, earlier treatment was significantly associated with shorter clinical courses (median, 2 days [interquartile range 1–3] vs. 7 days [4–10] vs. 10 days [5–15]; log-rank p < 0.001). Univariable and multivariable Cox regression analyses also demonstrated an independent effect of earlier nimodipine treatment on earlier remission of TCHs (adjusted hazard ratio, 0.75 per 1-day delay in treatment; 95% CI, 0.693–0.802, p < 0.001).

Conclusions: The clinical course of RCVS differed according to the timing of nimodipine treatment, suggesting the effect of earlier nimodipine treatment. In addition to preventing TCHs, beneficial effects of earlier nimodipine treatment on the progression of vasoconstriction and development of neurological complications should be investigated in future studies.

[Reversible cerebral vasoconstriction syndrome: a clinical study of 11 cases]

This study reports eleven cases of reversible cerebral vasospasm syndrome (RCVS). Of the 11 patients, two were males and nine were females, with the average age of 47.9 ± 14.1 years. Many of these patients were young. The rates of severe, intractable and pulsative headache, generalized convulsions, and motor hemiparesis were 64%, 27%, and 36%, respectively. As complications of intracerebral lesions in the early stage of disease onset, convexal subarachnoid hemorrhage, lobar intracerebral hemorrhage, and posterior reversible encephalopathy syndrome were observed in 63%, 9%, and 45% of cases, respectively. Cerebral infarction occurred in 45% of cases at around 1-3 weeks after onset. Improvement of cerebral vasoconstriction was recognized in several cases from about the first month of onset. The post-partum period, migraine, transfusion, rapid amelioration for anemia, renal failure, bathing, and cerebrovascular dissection were suspected as disease triggers. Abnormally high blood pressure at onset was confirmed in 55% of cases. It is important to analyze the pathophysiology of RCVS associated with these triggers from the viewpoint of the breakdown of the blood-brain barrier.

Clinical significance of centripetal propagation of vasoconstriction in patients with reversible cerebral vasoconstriction syndrome: A retrospective case-control study

Introduction

We previously reported centripetal propagation of vasoconstriction at the time of thunderclap headache remission in patients with reversible cerebral vasoconstriction syndrome. Here we examine the clinical significance of centripetal propagation of vasoconstriction.

Methods

Participants comprised 48 patients who underwent magnetic resonance angiography within 72 h of reversible cerebral vasoconstriction syndrome onset and within 48 h of thunderclap headache remission.

Results

In 24 of the 48 patients (50%), centripetal propagation of vasoconstriction occurred on magnetic resonance angiography at the time of thunderclap headache remission. The interval from first to last thunderclap headache in patients with centripetal propagation of vasoconstriction (14 ± 10 days) was significantly longer than that of patients without centripetal propagation of vasoconstriction (4 ± 2 days). In the patients with centripetal propagation of vasoconstriction at the time of thunderclap headache remission, the incidence of another cerebral lesion (38%, 9 of 24 cases) was significantly higher than in patients without centripetal propagation of vasoconstriction (0%). From findings of sequential magnetic resonance angiography before and after thunderclap headache remission, we observed tendencies in which centripetal propagation of vasoconstriction gradually progressed after the onset of reversible cerebral vasoconstriction syndrome and peaked at the time of thunderclap headache remission. The progress of centripetal propagation of vasoconstriction concluded with thunderclap headache remission.

Conclusions

Centripetal propagation of vasoconstriction has clinical significance as an indicator of the severity of reversible cerebral vasoconstriction syndrome. The presence of centripetal propagation of vasoconstriction is associated with an increased risk of brain lesions and a longer interval from first to last thunderclap headache. Moreover, repeat magnetic resonance angiography to assess centripetal propagation of vasoconstriction during the time from onset to thunderclap headache remission can help diagnose reversible cerebral vasoconstriction syndrome.

Serial testing of the ICHD-3 beta diagnostic criteria for probable reversible cerebral vasoconstriction syndrome: A prospective validation study

Objectives To serially test the International Classification of Headache Disorders (ICHD) 3rd edition beta version criteria for 6.7.3.1 probable reversible cerebral vasoconstriction syndrome (probable RCVS) in patients with thunderclap headache. Methods We prospectively screened consecutive patients with thunderclap headache who visited the Samsung Medical Center between October 2015 and March 2017. Patients were included in the analysis if they a) visited our hospital within 1 month after onset, b) completed a diagnostic work-up, and c) had no secondary causes other than RCVS. The ICHD-3 beta 6.7.3.1 criteria were evaluated serially during the first visit (visit 1), 2 weeks after the first visit (visit 2), and 1-3 months after onset (visit 3). Results A total of 99 patients completed this study. Based on the first clinical and radiological evaluation, 63 (63.6%) were diagnosed with angiogram-proven RCVS, whilst 36 (36.4%) showed normal neuroimaging. The ICHD-3 beta 6.7.3.1 criteria were fulfilled in 76.2% of patients with angiogram-proven RCVS. In patients with normal angiograms, the ICHD diagnosis of probable RCVS changed over time: 25.0%, 47.2%, and 38.9% at visits 1, 2, and 3, respectively. The sensitivity and specificity of the criteria at visit 1 were 72.4% and 95.5%, respectively, for the prediction of a final diagnosis of overall (angiogram-proven + probable) RCVS. Conclusions The ICHD-3 beta criteria for probable RCVS are applicable for patients with thunderclap headaches at the acute stage, with the exception of criterion C3. Criteria C1 and C2 are less reliable when applied at the first visit. Repeated evaluation is necessary to enhance diagnostic sensitivity.