A Pre-clinical Animal Model of Secondary Head and Neck Lymphedema

Abstract

Head and neck lymphedema (HNL) is a disfiguring disease affecting over 90% of patients treated for head and neck cancer. Animal models of lymphedema are used to test pharmacologic and microsurgical therapies; however, no animal model for HNL is described in the literature to date. In this study we describe the first reproducible rat model for HNL. Animals were subjected to two surgical protocols: (1) lymphadenectomy plus irradiation; and (2) sham surgery and no irradiation. Head and neck expansion was measured on post-operative days 15, 30 and 60. Magnetic resonance imaging (MRI) was acquired at the same time points. Lymphatic drainage was measured at day 60 via indocyanine green (ICG) lymphography, after which animals were sacrificed for histological analysis. Postsurgical lymphedema was observed 100% of the time. Compared to sham-operated animals, lymphadenectomy animals experienced significantly more head and neck swelling at all timepoints (P < 0.01). Lymphadenectomy animals had significantly slower lymphatic drainage for 6 days post-ICG injection (P < 0.05). Histological analysis of lymphadenectomy animals revealed 83% greater subcutis thickness (P = 0.008), 22% greater collagen deposition (P = 0.001), 110% greater TGFβ1+ cell density (P = 0.04), 1.7-fold increase in TGFβ1 mRNA expression (P = 0.03), and 114% greater T-cell infiltration (P = 0.005) compared to sham-operated animals. In conclusion, animals subjected to complete lymph node dissection and irradiation developed changes consistent with human clinical postsurgical HNL. This was evidenced by significant increase in all head and neck measurements, slower lymphatic drainage, subcutaneous tissue expansion, increased fibrosis, and increased inflammation compared to sham-operated animals.

Systematic review of head and neck lymphedema assessment

“…A host of other tape measurement protocols have been described, ranging from 3 to 11 tape measurements in total, each with very limited support in the literature 23–25,47,55–57 . As alternatives to tape measurements, digital photography with clinician analysis of serial photographs has been utilized in two studies 31,32 ; and electronic calipers were used in a recent animal model of HNL, though their use in the clinical setting has as yet not been published 12 …”

“…[23][24][25]47,[55][56][57] As alternatives to tape measurements, digital photography with clinician analysis of serial photographs has been utilized in two studies 31,32 ; and electronic calipers were used in a recent animal model of HNL, though their use in the clinical setting has as yet not been published. 12 For the purposes of diagnosis and classification, the key advantage of measurement protocols is their objectivity relative to rating scales, while still being easily performed at the bedside by a range of trained providers. This objectivity is significant, given that a meta-analysis of lymphedema of all types in 2010 reported that studies using objective methods of assessment were twice as likely to diagnose patients with lymphedema relative to studies using subjective methods.…”

“…Interestingly, magnetic resonance imaging (MRI) of the head and neck has not yet been utilized in the HNL literature outside of a single case report and a recent animal study, 12,45 likely due to limitations with access. This is despite the potential utility of MRI in volumetric analysis of soft tissues, providing greater detail on soft tissue abnormalities than does CT, and its demonstrated sensitivity and specificity for diagnosing extremity lymphedema.…”

“…[6][7][8][9][10] HNL is thought to occur due to treatment-related injury to the head and neck lymphatics, resulting in a disruption of normal lymphatic drainage and an accumulation of lymph fluid in the interstitial space. 11,12 Two subtypes have been distinguished: external HNL, present in the face, submental region and neck; and internal HNL, affecting structures of the oral cavity, pharynx and larynx. 8,13,14 Management of HNL has traditionally been centered on physiotherapy, involving manual lymphatic drainage Abbreviations: HNC, head and neck cancer; HNL, head and neck lymphedema.…”

“…Both neck dissection and radiotherapy have been implicated in the development of secondary HNL, with the use of multiple treatment modalities conferring a particularly increased risk 6–10 . HNL is thought to occur due to treatment‐related injury to the head and neck lymphatics, resulting in a disruption of normal lymphatic drainage and an accumulation of lymph fluid in the interstitial space 11,12 . Two subtypes have been distinguished: external HNL, present in the face, submental region and neck; and internal HNL, affecting structures of the oral cavity, pharynx and larynx 8,13, 14 …”