Neuroradiology (2003) 45: 631–633 DOI 10.1007/s00234-003-1062-5
T. Kendi O.K. Arıkan C. Koc¸
Received: 10 April 2003 Accepted: 11 June 2003 Published online: 25 July 2003 Ó Springer-Verlag 2003 T. Kendi (&) 15 sokak 37/10, Bahc¸elievler, Ankara, Turkey E-mail:
[email protected] Tel.: +90-312-2211622 Fax: +90-318-2252819 T. Kendi (&) Department of Radiology, Kırıkkale University School of Medicine, Kırıkkale, Turkey O.K. Arıkan Æ C. Koc¸ Department of Otorhinolaryngology, Kırıkkale University School of Medicine, Kırıkkale, Turkey
DIAGNOSTIC NEURORADIOLOGY
MR spectroscopy in a cervical abscess
Abstract MR spectroscopy (MRS) has been used to analyse noninvasively tissues at a molecular level. Hydrogen and phosphorus MRS have been used for characterisation of intracranial solid and cystic masses, gynaecological tumours and lymph nodes. We report a cystic, tick-walled mass in the soft tissues of the neck. Single-voxel proton MRS revealed a prominent acetate peak at 1.92 ppm and a diagnosis of abscess was suggested. At operation a pyogenic neck abscess was confirmed, with culture of the pus.
Introduction Proton MR spectroscopy (MRS) has been used for noninvasive investigation of metabolites. It an reveal malignant tumours which are clinically and radiologically occult [1]. In most solid intracranial tumours N-acetylaspartate (NAA) is decreased, choline (Cho) and lactate (Lac) increased. In differential diagnosis of cystic-appearing lesions of the head, gliomas, metastasis, arachnoid cysts, epidermoid cysts and abscesses may be considered. Most of these have a Lac signal as a nonspecific metabolite secondary to anaerobic metabolism. However, in brain abscesses MRS shows elevation of acetate and succinate, so that the spectrum is significantly different from that cystic or necrotic neoplasms [2]. MRS has also been used to investigate benign and malignant masses and lymph node metastasis in
Keywords Abscess Æ Neck Æ Magnetic resonance spectroscopy
the neck [1,3]. Squamous cell carcinoma showed an increased Cho/creatine (Cr) ratio as did metastatic lymph nodes, the latter also with a Lac peak. As far as we know, there has been no report of MRS of a soft-tissue neck abscess. We present the MRS findings in such a lesion and review the literature.
Case report A 37-year-old man had difficulty in swallowing and right-sided neck swelling over 1 month. Examination revealed swelling which was neither tender nor erythematous; there was no fever or leukocytosis. MRI and MRS were performed at 1.5 tesla, using an anterior neck coil. We obtained spin-echo T1- and T2-weighted images in three planes, plus contrast-enhanced coronal and axial T1-weighted images. A mass which gave low signal on T1- and high signal on-T2 weighted images, with a prominent surrounding wall, lay at the level of oropharynx, narrowing from the right. It extended to the
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b
Fig. 1 T2-weighted axial image shows a high-signal mass obliterating the oropharynx from the right and extending to the carotid and parapharyngeal spaces and prevertebral area. The apparently cystic mass has a thick wall. An 8 cm3 voxel for MR spectroscopy (MRS) was placed within the lesion (white square)
parapharyngeal space and prevertebral area posteriorly, and to the right carotid space, displacing the vessels (Fig. 1). The well-defined wall of this apparently cystic lesion showed prominent contrast enhancement. Single voxel MRS was performed with PRESS (TR 1500 TE 35 ms, 192 acquisitions, 8 cm3 voxel). The total time for imaging and spectroscopy was about 50 min. The spectrum had a prominent acetate peak at 1.92 ppm. There was no evidence of other metabolites such as Cho, Cr, myoinositol, NAA and other amino acids such as succinate (Fig. 2). Although other amino acid levels were not elevated, the prominent acetate peak led us to suggest an abscess. A surgery this diagnosis was confirmed, with culture of the purulent material.
Fig. 2 Proton MRS revealed a high acetate peak at 1.92 ppm (arrow)
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Discussion Proton MRS spectroscopy may be useful in differentiating tumours and lymph node metastases from normal muscle. The increased Cho/Cr in metastatic lymph nodes and Lac peak in cancer tissue, as compared with muscle, may be reliable criteria [3]. Although there are many reports of MRS of cystic and solid lesions of the brain, there have been few studies of the neck, mainly due to technical difficulties [1,3]. Increased Lac is accepted as a nonspecific finding in intracranial cysts. MRS of brain abscesses has demonstrated increased levels of Lac, acetate, succinate and amino acids including valine, alanine, and leucine, a pattern completely different from that of cystic or necrotic brain tumours. Increase in Lac, acetate, and succinate is presumably a result of enhanced glycolysis
and fermentation of the organisms [2]. MRI features are largely nonspecific as regards the causative organism in a brain abscess, but Gupta et al. [4] indicated revealed that with MRS it was possible to distinguish between pyogenic and tuberculous abscesses, the latter showing increased lipid levels, without Lac, succinate and acetate peaks. Differential diagnosis of cysts in the neck is wide. As far as we know MRS of a neck abscess has not been reported previously. In our case, the mass was adjacent to and compressing the oropharynx. MRI demonstration of a thick wall suggested an abscess, but the clinical findings did not support that. MRS demonstration of a high acetate peak did, however, lead us to diagnose an abscess, even in the absence of other expected metabolites such as Lac, succinate and amino acids.
References 1. Mukherji SK, Schiro S, Castillo M, et al (1996) Proton MR spectroscopy of squamous cell carcinoma of the upper aerodigestive tract: in vitro characteristics AJNR 17: 1485–1490
2. Chang KH, Song IC, Kim SH, et al (1998) In vivo single voxel proton MR spectroscopy in intracranial cystic masses. AJNR 19: 401–405 3. Star-Lack JM, Adalsteinsson E, Adam MF, et al (2000) In vivo H MR spectroscopy of human head and neck lymph node metastasis and comparison with oxygen tension measurements. AJNR 21: 183–193
4. Gupta RK, Vatsal DK, Husain N, et al (2001) Differentiation of tuberculous from pyogenic brain abscesses with in vivo proton MR spectroscopy and magnetization transfer imaging. AJNR 22: 1503–1509
