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 Table of Contents  
CASE REPORT
Year : 2019  |  Volume : 3  |  Issue : 3  |  Page : 94-96

Asymmetric tongue muscle uptake of F-18 fludeoxyglucose in a 75-year-old male patient with nasopharyngeal cancer: Possible marker for hypoglossal nerve injury


Department of Nuclear Medicine, King Fahad Medical City, Riyadh, Kingdom of Saudi Arabia

Date of Web Publication15-Oct-2019

Correspondence Address:
Dr. Intidhar El Bez
Department of Nuclear Medicine, King Fahad Medical City, P.O. Box. 59046, Riyadh 11525
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/LJMS.LJMS_37_19

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  Abstract 


A 75-year-old man, with nasopharyngeal cancer, had multiple metastases on 2-F-18 Fludeoxyglucose positron emission tomography imaging. The left hemitongue had increased activity as compared with the right. This was not the result of the presence of a metastasis to the tongue or underlying gross tumors, as shown by a negative magnetic resonance imaging brain and failure to demonstrate a lesion over a period of weeks. Uptake was likely related to the left hemiglossal muscle activity. This was made more apparent by decreased uptake on the right side of the tongue (up to the midline) as a result of cranial nerve hypoglossal injury.

Keywords: 2-F-18 Fludeoxyglucose, cranial nerve XII, positron emission tomography and computed tomography, tongue


How to cite this article:
El Bez I, Basha AC, Tulbah R, Alghmlas F, Alharbi M. Asymmetric tongue muscle uptake of F-18 fludeoxyglucose in a 75-year-old male patient with nasopharyngeal cancer: Possible marker for hypoglossal nerve injury. Libyan J Med Sci 2019;3:94-6

How to cite this URL:
El Bez I, Basha AC, Tulbah R, Alghmlas F, Alharbi M. Asymmetric tongue muscle uptake of F-18 fludeoxyglucose in a 75-year-old male patient with nasopharyngeal cancer: Possible marker for hypoglossal nerve injury. Libyan J Med Sci [serial online] 2019 [cited 2019 Nov 13];3:94-6. Available from: http://www.ljmsonline.com/text.asp?2019/3/3/94/269222




  Introduction Top


Two-F-18 Fludeoxyglucose (2-F-18 FDG) positron emission tomography and computed tomography (PET-CT) are a very important study for both staging and follow-up of oropharyngeal squamous cell carcinoma (SCC). It is significantly more sensitive than CT or magnetic resonance imaging (MRI) scan alone and allows for a noninvasive assessment of the response of chemoradiotherapy.[1] Asymmetrical FDG hypermetabolic uptake within the oropharynx is a feature of malignancy excluding compounding factors, such as infection or post-trauma changes. Taking into an account that physiological uptake can also lead to false-positive results.[2] There have only been few case reports documented in the literature of asymmetrical tongue muscle uptake of 2-F-18 FDG as a marker of hypoglossal nerve palsy.[3],[4] In fact, with the exception of the myocardium, muscle accumulation of 2-F-18 FDG is usually less than that of internal organs.[5],[6] We describe a case with a marked difference in 2-F-18 FDG activity between the right and left tongue muscles.


  Case Report Top


A 75-year-old gentleman, not diabetic, with a history of nasopharyngeal cancer T4N3M1, metastatic to bones as revealed on the baseline PET-CT. Six months after chemotherapy, he complained of dryness of mouth and left cranial nerve XII weakness. A follow-up PET-CT was performed, revealed residual intense hypermetabolic right parapharyngeal lymph node and residual low-grade uptake in homolateral cervical lymph node. There is also interval resolution of the previously noted FDG avid bone metastases; however, there is new development of prominent 2-F-18 FDG uptake of the tongue more on the left side, SUVmax was 10.9. Cross-sections of this area of the patient demonstrated a photopenic region, which encompassed the entire right side of the tongue, ending abruptly at the midline [Figure 1]. This was an unusual finding because regional uptake is usually symmetric, as demonstrated in the baseline PET-CT [Figure 2]. This was compatible with loss of innervation of the cranial nerve XII and its usual metabolic activity. The right side of the tongue did reveal metabolic function, with a possible compensatory increased activity. A CT of the head showed the right hemitongue fatty atrophy with compensatory enlargement of the muscles of the left hemitongue [Figure 3]. MRI of brain and sinuses was performed and did not reveal any oral tongue tumor, so the abnormal uptake seen on the PET-CT was correlated to denervation injury due to involvement of the skull base [Figure 4].
Figure 1: Follow-up positron emission tomography/computed tomography performed 6 months after chemotherapy (a) three-dimensional maximum intensity projection (b) axial (c) sagittal and (d) coronal views (left column: positron emission tomography, middle: fused, right: computed tomography) demonstrate increased fludeoxyglucose uptake in the left side of the tongue (red arrow). Unilateral muscular atrophy is apparent in the right half of the tongue (green arrow)

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Figure 2: Baseline positron emission tomography/computed tomography. Axial views (left column: positron emission tomography, middle: fused, right: computed tomography) demonstrate a large left level II hypermetabolic lymph node (green arrows). No abnormal uptake within the tongue was seen

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Figure 3: Axial contrast-enhanced computed tomography image showing right hemitongue fatty atrophy (arrow) with compensatory enlargement of the muscles of the left hemitongue

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Figure 4: Axial T1 (a) and T2 (b) images. No tumor was seen

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  Discussion Top


PET-CT scan is utilized frequently for surveillance following treatment for head and neck cancers. PET is typically performed with 2-F-18 FDG, which is a D-glucose analog. Hence, it is transported into the malignant cells by the same mechanism as glucose; however, the modified glucose molecule cannot be metabolized and becomes trapped within the cells. Increased vascularity, membrane transporters, and intracellular hexokinase coupled with low glucose-6-phosphatase in malignant cells lead to increased accumulation of 2-F-18 FDG. An augmented dependence on glucose metabolism is the principle behind imaging head and neck cancers with PET.[7],[8]

Various physiological and technical factors can affect FDG uptake in the tissues of interest.[7] A major pitfall of FDG PET is the physiologic variation in the radiotracer tissue uptake, especially in the head and neck. Muscles of the oral tongue variably accumulate FDG and moderate uptake can be seen in the anterior floor of mouth because of the genioglossus muscle, which prevents the tongue from falling back in the supine position.[8] This type of benign uptake is usually symmetric and diffuse. FDG uptake can be seen in the tongue because of muscular activity, for example, during talking and in benign pathology such as amyloidosis.[2],[9] Increased uptake also occurs after radiotherapy or surgery at the site of malignancy up to 6 months after the conclusion of treatment. Therefore, PET-CT is performed at least 8 weeks after treatment.[7]

Hypoglossal nerve palsy can result in denervation atrophy of the intrinsic and extrinsic lingual muscles. The muscles of the unaffected side may undergo compensatory hypertrophy. In our case, uniform uptake of FDG in the left tongue up to the midline was not related to a new primary SCC. The interval between treatment and PET-CT was sufficiently long to reduce inflammatory change after surgery and radiotherapy. The patient was not diabetic and was in compliance with the scanning protocol by avoiding voluntary tongue exercises prior to the scan. Anatomical imaging demonstrated an atrophic right hemitongue and a hypertrophied left hemitongue. No tumor was seen on either CT or MRI scans. These features were consistent with right hypoglossal palsy and compensatory increased muscular activity in the nonparalyzed tongue.[10] The tongue can be involved by other disease entities, for example, amyloidosis, but there is no evidence for such a disorder in this patient.[11] The tongue is involved in multiple events of neural connectivity [12] and has representation in the lateral cortical region of the brain.[13] Furthermore, the tongue plays a role in several oral and pharyngeal reflexes.[14] There are scant data, thus far, on imaging the tongue by means of 2-F-18 FDG in the course of these multiple disorders.

In summary, unspecific FDG uptake can mislead to wrong findings and final diagnosis, with the differentiation between FDG-avid malignant tissue and false-positive or nonspecific FDG uptake being especially difficult in patients with cancer of the head and neck.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Kitagawa Y, Nishizawa S, Sano K, Ogasawara T, Nakamura M, Sadato N, et al. Prospective comparison of 18F-FDG PET with conventional imaging modalities (MRI, CT, and 67Ga scintigraphy) in assessment of combined intraarterial chemotherapy and radiotherapy for head and neck carcinoma. J Nucl Med 2003;44:198-206.  Back to cited text no. 1
    
2.
Loevner LA, Kim AK, Mikityansky I. PET/CT-MR imaging in head and neck cancer including pitfalls and physiologic variations. PET Clin 2008;3:335-53.  Back to cited text no. 2
    
3.
Davis E, Solis V, Rosenberg RJ, Spencer RP. Asymmetric tongue muscle uptake of F-18 FDG: Possible marker for cranial nerve XII paralysis. Clin Nucl Med 2004;29:531-3.  Back to cited text no. 3
    
4.
Werner MK, Pfannenberg C, Öksüz MÖ. Nonspecific FDG uptake in the tongue mimicking the primary tumor in a patient with cancer of unknown primary. Clin Imaging 2011;35:405-7.  Back to cited text no. 4
    
5.
Ohkusu Y, Takahashi N, Ishikawa T, Sumita S, Kobayashi T, Matsushita K, et al. Effect of biventricular pacing on myocardial glucose metabolism in patients with heart failure using fluoro-18-deoxyglucose positron emission tomography. Pacing Clin Electrophysiol 2003;26:144-7.  Back to cited text no. 5
    
6.
Oi N, Iwaya T, Itoh M, Yamaguchi K, Tobimatsu Y, Fujimoto T, et al. FDG-PET imaging of lower extremity muscular activity during level walking. J Orthop Sci 2003;8:55-61.  Back to cited text no. 6
    
7.
Liu Y, Ghesani NV, Zuckier LS. Physiology and pathophysiology of incidental findings detected on FDG-PET scintigraphy. Semin Nucl Med 2010;40:294-315.  Back to cited text no. 7
    
8.
Abouzied MM, Crawford ES, Nabi HA 18F-FDG imaging: Pitfalls and artifacts. J Nucl Med Technol 2005;33:145-55.  Back to cited text no. 8
    
9.
Ariji Y, Fuwa N, Kodaira T, Tachibana H, Nakamura T, Satoh Y. False-positive positron emission tomography appearance with 18F-fluorodeoxyglucose after definitive radiotherapy for cancer of the mobile tongue. Br J Radiol 2009;82:e3-7.  Back to cited text no. 9
    
10.
Loh C, Maya MM, Go JL. Cranial nerve XII: The hypoglossal nerve. Semin Ultrasound CT MR 2002;23:256-65.  Back to cited text no. 10
    
11.
Malaguti MC, Plasmati R, Mascalchi M, Salvi F. Tongue involvement in amyloidoses. Neurology 2002;59:793.  Back to cited text no. 11
    
12.
He AG, Tan LH, Tang Y, James GA, Wright P, Eckert MA, et al. Modulation of neural connectivity during tongue movement and reading. Hum Brain Mapp 2003;18:222-32.  Back to cited text no. 12
    
13.
Rödel RM, Laskawi R, Markus H. Tongue representation in the lateral cortical motor region of the human brain as assessed by transcranial magnetic stimulation. Ann Otol Rhinol Laryngol 2003;112:71-6.  Back to cited text no. 13
    
14.
Miller AJ. Oral and pharyngeal reflexes in the mammalian nervous system: Their diverse range in complexity and the pivotal role of the tongue. Crit Rev Oral Biol Med 2002;13:409-25.  Back to cited text no. 14
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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