CLEANING THE BRAIN THROUGH TURBULENT GLYMPHATIC FLOW: THE WASHING MACHINE HYPOTHESIS

LYMPHSPIRATION: In a thought experiment, a "washing machine" model is proposed based on turbulent flow from complex multi-dimensional forces to characterize fluid dynamics in the brain. The glymphatic system's hypothetical role in this system is illustrated in a series of diagrams. Implications of this model are discussed in terms of normal physiology and a variety of pathologic conditions such as brain atrophy and Alzheimer disease.

IN MEMORIAM: Oldřich Eliška, MD, DrSc

Oldřich Eliška, MD, DrSc November 13, 1934 - July 12, 2021

METHODS FOR QUANTIFYING BREAST CANCER-RELATED LYMPHEDEMA IN PATIENTS UNDERGOING A CONTRALATERAL PROPHYLACTIC MASTECTOMY

Patients treated for breast cancer are at risk of developing breast cancer-related lymphedema (BCRL). A significant proportion of patients treated for breast cancer are opting to undergo a contralateral prophylactic mastectomy (CPM). Currently, it remains unclear as to whether the relative volume change (RVC) equation may be used as an alternative to the weight adjusted change (WAC) equation to quantify BCRL in patients who undergo CPM. In order to simplify BCRL screening, our cohort of patients who underwent a CPM (n=310) was matched by BMI to a subset of patients who underwent unilateral breast surgery (n=310). Arm volume measurements were obtained via an optoelectronic perometer preoperatively, postoperatively, and in the follow-up setting every 6-12 months. The correlation of ipsilateral RVC and WAC values for those who underwent bilateral surgery was calculated (r=0.60). Contralateral WAC values for patients in both cohorts were compared, and there was no significant difference between the two distributions in variance (p=0.446). The RVC equation shows potential to be used to quantify ipsilateral postoperative arm volume changes for patients who undergo a CPM. However, a larger trial in which RVC and WAC values are prospectively assessed is needed.

TREATMENT OF SECONDARY LOWER LIMB LYMPHEDEMA AFTER GYNECOLOGIC CANCER WITH COMPLEX DECONGESTIVE THERAPY

Secondary lower extremity lymphedema is a common complication of treatment for gynecological cancers. Conservative therapy plays an important role in the treatment of patients with secondary lower extremity lymphedema; in particular, complex decongestive therapy (CDT) has been recognized as an effective nonoperative technique for these patients. But CDT therapy for secondary lower extremity lymphedema remains a problem in China because this technique and its effectiveness have not achieved widespread use and popularity. Our goal was to assess effects of CDT in patients with secondary lower limb lymphedema after treatment for gynecological cancers. The retrospective study consisted of 60 patients who were treated with 20 sessions of CDT. Assessments included objective changes in limb circumference, degree of LE, imaging features, and incidence of erysipelas before and after CDT treatment. We found that CDT can effectively improve lymph stasis and promote backflow, and decrease circumference, interstitial fluid content, and incidence of erysipelas of lymphedematous lower limb. Our results demonstrate that CDT is an effective treatment method for patients with secondary lower limb lymphedema following treatment for gynecologic cancers. This technique should be more widely utilized and popularized in China to improve the quality of life of millions of patients with secondary lower limb lymphedema.

LYMPHEDEMA DURATION AS A PREDICTIVE FACTOR OF EFFICACY OF COMPLETE DECONGESTIVE THERAPY

Lymphedema is a common condition with global impact and a multitude of complications, however, only a few professionals specialize in its management. A retrospective analysis of 105 subjects with unilateral lymphedema upper or lower limb was performed to investigate whether the duration of lymphedema constitutes an important factor associated with the efficacy of complete decongestive therapy (CDT). Subjects were classified into two groups according to the duration of lymphedema, prior to CDT: group A (≤1 year) and group B (>1 year). Both groups were treated daily according to the same CDT protocol for four weeks. The CDT efficacy was determined based on the percent reduction of excess volume (PREV) measurements. Lymphedema was significantly reduced in both groups of subjects, but significantly more in group A (p<0.001). In subjects with upper limb lymphedema, median value of PREV was 80.8% (interquartile range, 79.1-105.0%) in group A and 62.0% (interquartile range, 56.7-66.5%) in group B (p<0.001). In subjects with lower limb lymphedema PREV was 80.7% (interquartile range, 74.9-85.2%) and 64.5% (interquartile range, 56.0-68.1%) for groups A and B, respectively (p<0.001). Duration of lymphedema was found to be a strong predictive factor that may significantly impact CDT efficacy. Therapeutic effects were increased in subjects who were detected and treated earlier for lymphedema.

POSSIBILITY OF NEW LYMPHATIC PATHWAY CREATION THROUGH NEO-LYMPHANGIOGENESIS INDUCED BY SUBDERMAL DISSECTION

Surgical intervention and subsequent wound healing process are known to induce neo-lymphangiogenesis, but few studies have been reported to utilize this mechanism for lymphedema treatment. The aim of this study was to evaluate feasibility of subdermal dissection for neo-lymphangiogenesis induction (SDN) to treat lower extremity lymphedema (LEL). Medical records of secondary LEL patients who had undergone ICG lymphography and SDN procedure were reviewed. SDN was performed by dissecting fat tissues just below the dermis from the most proximal area showing dermal backflow through abdominal-toaxillary lymphatic pathways. Perioperative lymphedematous conditions were evaluated with lymphedema quality of life score (LeQOLiS) and LEL index. Seventeen female patients were included. SDN could be performed in 10 minutes on average without postoperative complication. Postoperative ICG lymphography showed new lymphatic pathways in 6 (35.3%) cases. Postoperative LeQOLiS ranged from 9 to 66, which was statistically lower than preoperative LeQOLiS (32.9 ± 19.2 vs. 36.6 ± 19.3, p = 0.048), whereas there was no statistically significant difference between pre- and post-operative LEL index (275.2 ± 23.3 vs. 270.5 ± 20.8, P = 0.073). Subdermal dissection, although its probability is not high, has a potential to induce neo-lymphangiogenesis. Further studies are required to improve and demonstrate efficacy of the procedure for new lymphatic pathway creation.

ISL NEWS

2021 ISL News

ABNORMAL LYMPHATIC PHENOTYPE IN A CRISPR MOUSE MODEL OF THE HUMAN LYMPHEDEMA-CAUSING CONNEXIN47 R260C POINT MUTATION

Connexin proteins form gap junctions controlling exchange of ions and small molecules between cells and play an important role in movement of lymph within lymphatic vessels. Connexin47 (CX47) is highly expressed in lymphatic endothelial cells and CX47 missense mutations, i.e., R260C, cosegregate with primary lymphedema in humans. However, studies utilizing CX47 knockout mice have failed to demonstrate any lymphatic anomalies. To unravel the lymphatic consequences of expressing a mutant CX47 protein, we used CRISPR technology to create a mouse carrying a Cx47 missense mutation (Cx47R259C) equivalent to the human CX47R260C missense mutation associated with human primary lymphedema. Intradermal Evans Blue dye injection identified a 2-fold increase in regional lymph nodes in homozygous Cx47R259C mice compared to wildtype, particularly in the jugular region (4.8 ± 0.4 and 2.0 ± 0.0, respectively, p<0.01). Associated lymphatic channels were increased in Cx47R259C mice and mesenteric lymph reflux occurred in homozygous Cx47R259C mice but not in wildtype. Contractility of superficial cervical lymphatics, assessed by pressure myography, was reduced in homozygous Cx47R259C mice compared to wildtype. In conclusion, our data are the first to demonstrate a role for the Cx47 protein in lymphatic anatomy and function. This phenotype is similar to that found with other valve deficient mouse mutants, e.g., in Foxc2. Of significance, this study is the first to use CRISPR technology to develop a pre-clinical model of primary lymphedema and demonstrates the importance of distinguishing between lack of and presence of mutant protein when developing clinically relevant animal models for translation of pre-clinical findings.

ASSESSMENT OF LYMPHEDEMA WITH LYMPHOSCINTIGRAPHY: CAN NODAL QUANTIFICATION HELP?

Lymphoscintigraphy with combined qualitative and quantitative analysis is reported to be a more sensitive approach to diagnose lymphedema in comparison with the conventional clinical analysis. Our study seeks to evaluate the diagnostic performance of lower limb lymphoscintigraphy with amalgamation of qualitative and quantitative analysis by measuring the ilio-inguinal nodal uptake. This prospective observational study was comprised of 86 patients (172 limbs) diagnosed with lower limb lymphedema. After a thorough clinical grading of edema, radionuclide lymphoscintigraphy was performed as per a dedicated institutional protocol. Ilio-inguinal nodal quantification of tracer uptake was computed along with the visual study of the scans. Additionally, the corresponding mean nodal uptake percentage for each grade of lymphedema was assessed and a cut off nodal uptake percentage to differentiate between normal and abnormal limbs was defined. Although quantitative analysis with nodal uptake percentage provides objective criteria to diagnose lymphedema, it can only act as an adjunct to qualitative method without replacing it. Finally, standardization of procedure for quantitative lymphoscintigraphy is needed including the potential for combining both rate of clearance of tracer from injection site and nodal uptake for quantification.