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Letters to the Editor  |   April 2016
Response
Author Notes
  • Chair, Internal Medicine, Liberty University College of Osteopathic Medicine, Lynchburg, Virginia 
Article Information
Neuromusculoskeletal Disorders / Osteopathic Manipulative Treatment
Letters to the Editor   |   April 2016
Response
The Journal of the American Osteopathic Association, April 2016, Vol. 116, 200. doi:10.7556/jaoa.2016.041
The Journal of the American Osteopathic Association, April 2016, Vol. 116, 200. doi:10.7556/jaoa.2016.041
Heemstra points out some key citations worthy of a lengthier conversation on lymphatics in the central nervous system (CNS).1 She suggests that there is enough existing literature to support the existence of lymphatics and drainage in the CNS; however, I disagree. 
Unfortunately, I was not able to access the edition of Gray ’s Anatomy that she cites in her letter. Most anatomy textbooks and literature that I have referred to clearly state that there is not enough evidence to support lymphatics in the CNS. For example, in Junqueira’s Basic Histology, Mescher states, “With exceptions such as the bone marrow and most of the CNS (central nervous system), most tissues with blood microvascula-ture also contain lymphatic capillaries (or lympathics).”2 
Also, in a 2015 article, Iliff et al3(p977) state that “the apparent absence of conventional lymphatic vessels from the CNS has remained a persistent mystery of neurosci-ence, particularly in light of the exquisite sensitivity of neurons to the composition of their extracellular environment.” 
I believe there is enough evidence here to say that lymphatic drainage of the CNS was either thought to be nonexistent, done through another means, or believed to be a mystery. Much of the osteopathic manipulative treatment techniques that osteopathic physicians have been taught focus on promoting adequate lymphatic drainage from the head and neck (eg, osteopathic cranial manipulative medicine). If the article by Louveau et al4 does not help to validate part of osteopathic principles and practice, then it certainly goes a long way to help support it. 
References
Heemstra VL. Landmark article supports osteopathic medicine? setting the record straight [letter]. J Am Osteopath Assoc. 2016;116(4):200. doi:10.7556/jaoa.2016.040.
Mescher AL. The circulatory system. In: Mescher AL. Junqueira's Basic Histology. 14th ed. New York, NY: McGraw-Hill; 2016. http://accessmedicine.mhmedical.com/content.aspx?bookid=1687&Sectionid=109633081. Accessed February 14, 2016.
Iliff JJ, Goldman SA, Nedergaard M. Implications of the discovery of brain lymphatic pathways. Lancet Neurol. 2015;14(10):977-979. doi:10.1016/S1474-4422(15)00221-5. [CrossRef] [PubMed]
Louveau A, Smirnov I, Keyes TJ, et al Structural and functional features of central nervous system lymphatic vessels [published online June 1, 2015]. Nature. 2015;523(7560); 337-341. doi:10.1038/nature14432. [CrossRef] [PubMed]