Unilateral Vocal Cord Paralysis Causes Contralateral False-Positive Positron Emission Tomography Scans of the Larynx

Increased 18F-FDG Uptake in the Posterior Region of Contralateral Vocal Folds in Beagle Dogs With Unilateral Vocal Fold Immobility Disorders

OBJECTIVE

To explore the glycolytic metabolism of contralateral vocal fold compensation by examining the glycolytic metabolism of the posterior region of vocal folds in beagles with unilateral vocal fold immobility disorders and its correlation with acoustic parameters.

STUDY DESIGN

Prospective animal study.

SETTING

Department of Voice METHODS: Ten adult beagles were divided randomly into three groups: a unilateral cricoarytenoid joint dislocation (UCAJD) group (n = 4), a unilateral vocal fold paralysis (UVFP) group (n = 4), and a control group (n = 2). Positron emission tomography-computed tomography (PET/CT) scans of larynx and recordings of vocalizations were collected 4 months after the operations. The maximum standardized uptake values (SUVmax) of 18F-FDG within each posterior region of the vocal folds were obtained from PET/CT and voice recordings were analyzed for acoustic parameters F0, jitter, shimmer, and loudness using PRAAT.

RESULTS

In both UCAJD and UVFP groups, a significant increase of SUVmax was observed in the contralateral vocal fold relative to the impaired fold (P < 0.05). The SUVmax values of the contralateral vocal folds and the SUVmax values of the impaired vocal folds in the UCAJD, UVFP, and control groups were both found to be significantly different (P < 0.05). The SUVmax of the contralateral vocal fold may exhibit a potentially negative correlation with jitter and shimmer, with R2 values of 0.42 and 0.26 and P values of 0.03 and 0.11, respectively.

CONCLUSION

UCAJD and UVFP can cause enhanced glycolytic metabolism of the contralateral vocal fold relative to the impaired vocal fold. The SUVmax of the contralateral vocal fold may be positively correlated with acoustic quality.

Compensatory Movement of Contralateral Vocal Folds in Patients With Unilateral Vocal Fold Paralysis

OBJECTIVES

Previous studies of subjects with unilateral vocal fold paralysis (UVFP) as observed in a positron emission tomography-computed tomography (PET-CT) examination have demonstrated false positive results in the contralateral cricoarytenoid, in which the metabolism may be higher. This area may also be the site of contralateral compensatory movement in these patients. In this study, we compared the adduction speed of the contralateral vocal folds in patients with UVFP and in healthy subjects as measured by the stroboscopic laryngoscope frame rate. This study aimed to explore the contralateral compensatory movement of the vocal folds in subjects with UVFP.

METHODS

(1) We collected visual data from 14 patients with UVFP and 14 healthy subjects through a stroboscopic laryngoscope. These subjects were divided into a vocal fold paralysis group and a control group, and we analyzed the excessive adduction of the contralateral vocal folds in the vocal fold paralysis group by examining vocal fold movement speed (pixels/s) as featured in a stroboscopic laryngoscope video. (2) We analyzed the uptake of 18-FDG in the posterior vocal fold from positron emission tomography-computed tomography imaging from four subjects with UVFP and 12 healthy subjects. An independent sample t test and a χ² test were used to compare data.

RESULTS

Four subjects with UVFP had a higher metabolic rate in the contralateral cricoarytenoid joints, with a significant difference between the two groups, P < 0.05. Fifty percent of the cases of contralateral adduction of the vocal folds in the subjects with UVFP adducted past the midline, with a significant difference between the two groups, P < 0.05. The contralateral adduction of the vocal folds in subjects with UVFP had shorter video frames and higher adduction speed than the control group, and the difference was statistically significant, P < 0.05. There were fewer vocal fold abduction video frames and higher abduction speed of the healthy side of the vocal fold in subjects with UVFP than the control group, but there was no statistically significant difference, P > 0.05.

CONCLUSION

Subjects with UVFP exhibited faster adduction compensation in the contralateral vocal folds, and the contralateral cricoarytenoid joint's metabolism in subjects with UVFP was higher. These data may help clarify the diagnostic criteria for laryngeal nerve damage.

Incidence and Significance of Hypermetabolic PET-CT Findings in Unilateral TVF Motion Impairment

OBJECTIVE

To determine the incidence and significance of asymmetric hypermetabolic laryngeal findings on positron emission tomography-computed tomography (PET-CT) in patients with unilateral true vocal fold (TVF) motion abnormalities.

STUDY DESIGN

Retrospective cohort.

SETTING

Single-center tertiary care institution.

SUBJECTS AND METHODS

The medical records of patients with unilateral TVF motion abnormalities were reviewed. The incidence of normal and asymmetric hypermetabolic laryngeal findings was calculated in patients who underwent PET-CT and laryngeal examination, operative laryngoscopy with biopsy, or injection medialization laryngoplasty.

RESULTS

A total of 135 patients with unilateral TVF motion abnormalities underwent PET-CT. After exclusion of patients who completed new or surveillance imaging for a laryngeal neoplasm (n = 27), asymmetric hypermetabolic findings in the larynx were noted in 21 (19%) cases: 13 (12%) on the contralateral side of the impaired TVF, 8 (7%) on the ipsilateral side. Two (25%) patients with ipsilateral hypermetabolism had concerning subsequent fiberoptic laryngeal examinations prompting operative biopsy. There was no evidence of inflammatory or neoplastic disease in all patients with contralateral hypermetabolic findings. Fifteen patients completed PET-CT scans after injection medialization procedures; 6 (40%) displayed avidity ipsilateral to the side of the injection. The median time from injection to scan was 27 days, as opposed to 193 days in the unremarkable scans (P = .011).

CONCLUSION

Contralateral hypermetabolism in patients with unilateral TVF motion abnormalities may represent a false-positive finding. Ipsilateral hypermetabolic uptake without recent fold instrumentation warrants prompt diagnostic evaluation.

Positron-emission tomography enhancement after vocal fold injection medialization

The potential for the misinterpretation of positron-emission tomography (PET) scans in the context of a possible malignancy has been confirmed in a case report showing increased 18F-fluorodeoxyglucose (FDG) uptake after unilateral vocal fold augmentation medialization. We sought to expand these findings by investigating FDG uptake in a larger cohort of patients via a retrospective chart review. We examined the records of 15 adults-8 men and 7 women-who had undergone vocal fold augmentation for unilateral vocal fold paralysis and at least one subsequent PET scan. The differences in PET standard uptake value (SUV) between the injected and noninjected vocal folds were assessed via the Wilcoxon signed-rank test. A Spearman rank correlation coefficient was then used to estimate the relationship between differences in PET uptake and the length of time between the injection and the follow-up PET scan. The mean SUV of the injected vocal folds was 3.70, and the mean in the noninjected folds was 2.97. The difference did not achieve statistical significance (p = 0.34). In addition, the rank correlation coefficient with regard to the association between the difference in PET uptake and the duration between injection and PET was -0.24, suggesting an inverse relationship. However, the correlation coefficient did not differ significantly from zero (p = 0.34). We conclude that PET uptake after vocal fold augmentation medialization is variable and that it can increase substantially. This information should be considered in the context of the diagnostic accuracy of malignancy on PET.

An analysis of true- and false-positive results of vocal fold uptake in positron emission tomography-computed tomography imaging

Objectives:

Positron emission tomography-computed tomography with fluorine-18 fluorodeoxy-D-glucose has a major role in the investigation of head and neck cancers. Fluorine-18 fluorodeoxy-D-glucose is not a tumour-specific tracer and can also accumulate in benign pathology. Therefore, positron emission tomography-computed tomography scan interpretation difficulties are common in the head and neck, which can produce false-positive results. This study aimed to investigate patients detected as having abnormal vocal fold uptake on fluorine-18 fluorodeoxy-D-glucose positron emission tomography-computed tomography.

Methods:

Positron emission tomography-computed tomography scans were identified over a 15-month period where reports contained evidence of unilateral vocal fold uptake or vocal fold pathology. Patients’ notes and laryngoscopy results were analysed.

Results:

Forty-six patients were identified as having abnormal vocal fold uptake on positron emission tomography-computed tomography. Twenty-three patients underwent positron emission tomography-computed tomography and flexible laryngoscopy: 61 per cent of patients had true-positive positron emission tomography-computed tomography scans and 39 per cent had false-positive scan results.

Conclusion:

Most patients referred to ENT for abnormal findings on positron emission tomography-computed tomography scans had true-positive findings. Asymmetrical fluorine-18 fluorodeoxy-D-glucose uptake should raise suspicion of vocal fold pathology, accepting a false-positive rate of approximately 40 per cent.

End-organ radiographic manifestations of cranial neuropathies: A concise review

BACKGROUND

Cranial neuropathies are a spectrum of disorders associated with dysfunction of one or more of the twelve cranial nerves and the subsequent anatomic structures they innervate.

OBJECTIVE

The purpose of this article is to review radiographic imaging findings of end-organ aberrations secondary to cranial neuropathies.

METHOD

All articles related to cranial neuropathies were retrieved through the PubMed MEDLINE NCBI database from January 1, 1991 to August 31, 2014. These manuscripts were analyzed for their relation to cranial nerve end-organ disease pathogenesis and radiographic imaging.

RESULTS

The present review reveals detectable end-organ changes on CT and/or MRI for the following cranial nerves: olfactory nerve, optic nerve, oculomotor nerve, trochlear nerve, trigeminal nerve, abducens nerve, facial nerve, vestibulocochlear nerve, glossopharyngeal nerve, vagus nerve, accessory nerve, and hypoglossal nerve.

CONCLUSION

Radiographic imaging can assist in the detailed evaluation of end-organ involvement, often revealing a corresponding cranial nerve injury with high sensitivity and diagnostic accuracy. A thorough understanding of the distal manifestations of cranial nerve disease can optimize early pathologic detection as well as dictate further clinical management.

Left Vocal Cord Paralysis Detected by PET/CT in a Case of Lung Cancer

We report a patient with lung cancer. The first PET/CT imaging revealed hypermetabolic mass in the left aortopulmonary region and hypermetabolic nodule in the anterior segment of the upper lobe of the left lung. After completing chemotherapy and radiotherapy against the primary mass in the left lung, the patient underwent a second PET/CT examination for evaluation of treatment response. This test demonstrated, compared with the first PET/CT, an increase in the size and metabolic activity of the primary mass in the left lung in addition to multiple, pathologic-sized, hypermetabolic metastatic lymph nodes as well as multiple metastatic sclerotic areas in bones. These findings were interpreted as progressive disease. In addition, an asymmetrical FDG uptake was noticed at the level of right vocal cord. During follow-up, a laryngoscopy was performed, which demonstrated left vocal cord paralysis with no apparent mass. Thus, we attributed the paralytic appearance of the left vocal cord to infiltration of the left recurrent laryngeal nerve by the primary mass located in the apical region of the left lung. In conclusion, the knowledge of this pitfall is important to avoid false-positive PET results.

Hypoglossal nerve paralysis results in hypermetabolic activity on positron emission tomography/computed tomography in the contralateral tongue

False-positive results on combined positron emission tomography/computed tomography can complicate detection and surveillance of head and neck cancers. We present a rare case of false-positive contralateral [18F]-2-fluoro-2-deoxy-D-glucose tongue uptake after hypoglossal nerve paralysis caused by squamous cell carcinoma originating from the base of the tongue.

Metabolic activity of the tongue in obstructive sleep apnea. A novel application of FDG positron emission tomography imaging

RATIONALE

The metabolic activity of the tongue is unknown in patients with obstructive sleep apnea (OSA). Tongue electromyographic (EMG) activity is increased in patients with OSA. This increase in tongue EMG activity is thought to be related to either increased neuromuscular compensation or denervation with subsequent reinnervation of the muscle fibers. Increased glucose uptake in the tongue would support increased neuromuscular compensation, whereas decreased glucose uptake in the tongue would support denervation with subsequent reinnervation of the muscle fibers.

OBJECTIVES

To investigate the metabolic activity of the genioglossus and control upper airway muscles in obese patients with sleep apnea compared with obese control subjects.

METHODS

Obese subjects with and without OSA underwent a standard overnight sleep study to determine an apnea-hypopnea index. Each subject had a positron emission tomography with [(18)F]-2-fluoro-2-deoxy-D-glucose scan in addition to noncontrast computed tomography or magnetic resonance imaging. Glucose uptake was quantified within upper airway tissues with the standardized uptake value.

MEASUREMENTS AND MAIN RESULTS

We recruited 30 obese control subjects (apnea-hypopnea index, 4.7 ± 3.1 events per hour) and 72 obese patients with sleep apnea (apnea-hypopnea index, 43.5 ± 28.0 events per hour). Independent of age, body mass index, sex, and race, patients with OSA had significantly reduced glucose uptake in the genioglossus (P = 0.03) in comparison with obese normal subjects. No differences in standardized uptake value were found in the control muscles (masseter [P = 0.38] and pterygoid [P = 0.70]) and subcutaneous fat deposits (neck [P = 0.44] and submental [P = 0.95]) between patients with OSA and control subjects.

CONCLUSIONS

There was significantly reduced glucose uptake in the genioglossus of patients with sleep apnea in comparison with obese normal subjects with [(18)F]-2-fluoro-2-deoxy-D-glucose positron emission tomography imaging. The reduction in glucose uptake was likely secondary to alterations in tongue muscle fiber-type or secondary to chronic denervation. The reduced glucose uptake argues against the neuromuscular compensation hypothesis explaining the increase in tongue EMG activity in obese patients with OSA.

Reevaluation of FDG-PET/CT in patients with hoarseness caused by vocal cord palsy

OBJECTIVE

Vocal cord palsy (VCP) is a potential cause of hoarseness that results in decreasing mobility of the vocal cord. VCP can arise from a variety of causes; so, systematic screening is warranted for the management of patients with VCP. Asymmetrical fluorodeoxyglucose (FDG) uptake in vocal cords is a well-known feature in patients with VCP, but no detailed analysis has been performed. This study aimed at reevaluating the (18)F-FDG positron emission tomography/computed tomography (PET/CT) for patients with VCP.

METHODS

We retrospectively surveyed the results of FDG-PET/CT for 59 patients with VCP, compared to laryngoscopic findings. Quantitative analysis was performed using maximum standardized uptake value (SUVmax), and regions of interest were drawn over bilateral vocal cords as confirmed from the CT portion of PET/CT. Patients were divided into 3 groups: Group 1 (n = 14), in which VCP was caused by the lesion of the laryngeal area; Group 2 (n = 40), in which VCP was caused by the lesion on the root of the recurrent laryngeal nerve; and Group 3 (n = 5), in which VCP was caused by the lesion from the vagal center to the proximal vagus nerve.

RESULTS

For Group 1, higher FDG uptake in the paralyzed vocal cord was seen in 86 % of patients (mean SUVmax 8.1 ± 5.3 vs. 2.3 ± 0.4, paralyzed vs. non-paralyzed, respectively; P < 0.002). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 79 % for Group 1. Group 2 showed dominant FDG uptake in the non-paralyzed vocal cord (mean SUVmax 2.1 ± 0.9 vs. 1.5 ± 0.4, non-paralyzed vs. paralyzed, respectively; P < 0.001). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 93 % for Group 2. Group 3 showed no statistically significant difference in FDG accumulation between non-paralyzed and paralyzed vocal cords (mean SUVmax 1.8 ± 0.3 vs. 1.7 ± 0.3, non- paralyzed vs. paralyzed, respectively; P = 0.30). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 60 % for Group 3.

CONCLUSIONS

FDG accumulation in the vocal cords is dependent on the lesion site causing VCP. In addition, FDG-PET/CT can contribute to identification of the lesion responsible for inducing VCP.

Physiology and pathophysiology of incidental findings detected on FDG-PET scintigraphy

A routine feature of positron emission tomography/computed tomography (PET/CT) imaging is whole-body acquisition that results in many unexpected findings identified outside of the primary region of abnormality. Furthermore, (18)F-fluorodeoxyglucose (FDG) is a marker of glycolysis and does not specifically accumulate in malignancy. Understanding the physiology and pathophysiology of normal FDG distribution and common incidental findings is therefore essential to the physician interpreting whole-body FDG-PET/CT studies. Whereas many incidental findings are benign and of limited clinical significance, others represent uncommon manifestations of the primary malignancy, second malignancies, or various clinically significant pathologic processes. Patients with a single malignancy are at greater risk of developing synchronous or metachronous second malignancies, possibly related to exposure to shared carcinogenic agents or presence of prooncogenic mutations. The decision of how to pursue an intervention on the basis of an incidental finding is generally left to clinical judgment.

PET/CT-MR Imaging in Head and Neck Cancer Including Pitfalls and Physiologic Variations

This article emphasizes the strengths and potential pitfalls of functional and anatomic imaging in patients who have head and neck cancer with an emphasis on the treated neck, including patients who have undergone surgery and/or radiation therapy. Anatomic and molecular imaging together allow optimal evaluation and interpretation of a patient who has cancer. Effective assessment of patients who have head and neck cancer can be achieved through a careful review of pertinent anatomy, with awareness of the physiologic variations (especially those in the treated head and neck) seen in PET imaging, and analysis of both the PET and cross-sectional images.

Combined [18F]Fluorodeoxyglucose Positron Emission Tomography and Computed Tomography (FDG-PET/CT) for Detection of Recurrent, 131I-Negative Thyroid Cancer

BACKGROUND

Whole-body (131)I scintigraphy (WBS) and serial thyroglobulin measurement (Tg) are standard methods for detecting thyroid cancer recurrence after total/near total thyroidectomy and (131)I ablation. Some patients develop elevated Tg (Tg-positive) or there is clinical suspicion of recurrence, but WBS are negative (WBS-negative). This may reflect non-iodine-avid recurrence or metastasis. In 2002, the Centers for Medicare and Medicaid Services (CMS) approved positron emission tomography with [(18)F]fluorodeoxyglucose (FDG-PET) for Tg-positive/WBS-negative patients with follicular-cell-origin thyroid cancer. Limited data are available regarding the performance of combined FDG-PET/computed tomography (FDG-PET/CT) for detecting recurrent thyroid cancer in WBS-neg patients.

METHODS

This retrospective review of prospectively collected data analyzed 65 patients who had FDG-PET/CT for suspected thyroid cancer recurrence (April 1998-August 2006). Patients were WBS-negative but were suspected to have recurrence based on Tg levels or clinical grounds. Suspected FDG-PET/CT abnormalities were reported as benign or malignant. Lesions were ultimately declared benign or malignant by surgical pathology or clinical outcome (disease progression).

RESULTS

Of 65 patients who underwent FDG-PET/CT, 47 had positive FDG-PET/CT. Of the positive FDG-PET/CT, 43 studies were true positives, with 21 (49%) confirmed pathologically by surgical resection. The four false positives (3/4 confirmed pathologically) included an infundibular cyst, an inflamed supraclavicular cyst, pneumonitis, and degenerative disc disease. Of the 18 FDG-PET/CT studies that were negative, 17 were true negatives and one was a false negative (metastatic papillary carcinoma). Thus, FDG-PET/CT demonstrated a patient-based sensitivity of 98%, specificity of 81%, positive predictive value of 91%, and negative predictive value of 94%.

CONCLUSIONS

FDG-PET/CT is useful for detecting thyroid cancer recurrence in WBS-negative patients, and can assist decision making.

The role of PET in follow-up of patients treated for differentiated epithelial thyroid cancers

This article provides an update on the use of 2-[(18)F]-fluoro-2-deoxyglucose PET in the follow-up of patients treated for differentiated thyroid carcinoma (DTC). Although DTC recurrence is principally identified by a detectable basal or TSH-stimulated thyroglobulin level, PET helps to localize recurrent disease in patients with normal (131)I total-body scans and other normal anatomic imaging studies. The sensitivity of PET for localization of recurrence ranges from 45% to 100% according to tumor burden and differentiation. Whether PET should be performed after TSH stimulation is unclear, but several studies have reported an increase in the number of lesions detected by uptake of 2-[(18)F]-fluoro-2-deoxyglucose in this setting. Dependent on a center's approach, PET can alter therapeutic management in 9-51% of cases. Furthermore, PET might have a prognostic impact on survival in patients with metastatic disease and aid clinicians in selecting patients who need closer follow-up or aggressive treatment. PET can, therefore, be used advantageously in the follow-up of patients with DTC and can localize disease in patients with elevated thyroglobulin levels, normal total-body scans, and normal findings on conventional imaging modalities. In patients in whom local treatment is planned, especially those with aggressive pathologic variants of thyroid cancer, PET can exclude distant metastases. In patients with metastatic disease, PET can help to identify patients needing closer follow-up.