Citation Nr: 21005576 Decision Date: 02/02/21 Archive Date: 02/02/21 DOCKET NO. 14-41 666 DATE: February 2, 2021 ORDER Entitlement to service connection for prostate cancer, to include as due to asbestos exposure, in-service duties and exposure to the chemicals, and exposure related to Project Shipboard Hazard and Defense (SHAD) is denied. Entitlement to service connection for erectile dysfunction, to include as secondary to prostate cancer is denied. Entitlement to service connection for a respiratory disorder, to include as due to asbestos exposure, in-service duties and exposure to the chemicals, and exposure related to SHAD is denied. Entitlement to service connection for essential tremors, to include as due to asbestos exposure, in-service duties and exposure to the chemicals, and exposure related to SHAD is denied. FINDINGS OF FACT 1. The Veteran’s prostate cancer was not incurred in, and is not otherwise related to, his active service. 2. The Veteran’s erectile dysfunction is not etiologically related to his active military service. 3. The Veteran’s respiratory condition was not incurred in, and is not otherwise related to, his active service. 4. The Veteran’s essential tremors are a congenital disease that was not aggravated beyond natural progression during service. CONCLUSIONS OF LAW 1. The criteria for service connection for prostate cancer have not been met. 38 U.S.C. §§ 1110, 5103; 38 C.F.R. §§ 3.102, 3.303, 3.307, 3.309. 2. The criteria for service connection for erectile dysfunction, to include as secondary to prostate cancer have not been met. 38 U.S.C. §§ 1110, 5103; 38 C.F.R. §§ 3.102, 3.303, 3.304, 3.310. 3. The criteria for service connection for a respiratory disorder have not been met. 38 U.S.C. §§ 1110, 5103; 38 C.F.R. §§ 3.102, 3.303, 3.304. 4. The criteria for service connection for essential tremors have not been met. 38 U.S.C. §§ 101, 1131, 5107; 38 C.F.R. §§ 3.102, 3.303, 3.306. REASONS AND BASES FOR FINDINGS AND CONCLUSIONS The Veteran had active duty service from July 1965 to June 1967. The Veteran also had service with the Naval Reserves from July 1963 to July 1965, and July 1967 to October 1979 with several periods of active duty for training (ACDUTRA). This matter comes before the Board of Veterans’ Appeals (Board) on appeal from an October 2012 rating decision of a Department of Veterans Affairs (VA) Regional Office (RO). In September 2018, the Veteran testified at a hearing before the undersigned Veterans Law Judge (VLJ); a transcript is of record. The Board remanded the claims on appeal in April 2019 for additional development. The Board’s remand directives have been substantially completed. See Stegall v. West, 11 Vet. App. 268 (1998). This appeal has been advanced on the Board’s docket pursuant to 38 C.F.R. § 20.900(c); 38 U.S.C. § 7107(a)(2). Service Connection Service connection may be granted for a disability resulting from disease or injury incurred in or aggravated during active service. 38 U.S.C. § 1110; 38 C.F.R. § 3.303(a). Generally, to establish service connection, there must be competent, credible evidence of 1) a current disability, 2) in-service incurrence or aggravation of an injury or disease, and 3) a nexus, or link, between the current disability and the in-service disease or injury. See Davidson v. Shinseki, 581 F.3d 1313 (Fed. Cir. 2009). Where there is a chronic disease shown as such in service or within the presumptive period under 38 C.F.R. § 3.307, so as to permit a finding of service connection, subsequent manifestations of the same chronic disease at any later date, however remote, are service-connected, unless clearly attributable to intercurrent causes. If there is no showing of a resulting chronic condition during service, then a showing of continuity of symptomatology after service is required to support a finding of chronicity. 38 C.F.R. § 3.303(b). Service connection may be established for chronic diseases, to include cancer, manifesting to a certain degree within a year after service. 38 U.S.C. §§ 1112, 1113, 1137; 38 C.F.R. §§ 3.303, 3.304, 3.307, 3.309(a). In addition to service connection on a direct basis, service connection may also be granted for a disability that is proximately due to or aggravated by a service-connected disease or injury. 38 C.F.R. § 3.310; see also Allen v. Brown, 7 Vet. App. 439 (1995). 1. Entitlement to service connection for prostate cancer and erectile dysfunction. The Veteran seeks service connection for prostate cancer and erectile dysfunction. For the reasons that follow, the Board finds that service connection is not warranted for either condition. There is no dispute that the Veteran has had diagnoses of prostate cancer and erectile dysfunction during the course of this appeal. See July 2012 and August 2020 VA examinations. As such, the first element of service connection has been established. The Veteran contends that his conditions are related to a number of exposures in service. Primarily, the Veteran contends that he was exposed to a number of toxins during his participation in SHAD. As noted in the April 2019 remand, the Veteran’s participation in two SHAD tests has been conceded. The following substances were used in the SHAD tests the Veteran participated: VX nerve agent, diethyl phthalate, escherichia coli, serratia marcescens, bacillus globigii, calcofluor, and zinc cadmium sulfide. Accordingly, the Veteran’s exposure to these substances is conceded. The Veteran also contends that he was exposed to asbestos while aboard the U.S.S. George Easton. Given the Veteran’s active Navy service aboard a naval ship, the Board resolves all reasonable doubt in his favor and concedes exposure to asbestos. The Veteran alternatively contends that his conditions are related to chemicals/exposures that he encountered in performing his duties on the U.S.S. George Easton and in training. Specifically, he contends that he was exposed to lead paint, cigarette smoke, high temperatures, tear gas, and other shipboard contaminates. See July 2012 correspondence. He asserts that he encountered a number of these exposures while performing duties as a seaman and yeoman such as scraping and painting on the deck of the ship, working in an evaporation room, and scraping and painting the ship’s office and engineer log room. See September 2018 hearing transcript. He asserts that he was exposed to tear gas during training. The Board finds no reason to doubt the credibility of the Veteran’s statements and finds the assertions generally consistent with the circumstances, conditions, and hardships of his service as a seaman and yeoman. Accordingly, such exposures also are conceded. At various times throughout the appeal period, the Veteran also has indicated that his conditions may be due to a vaccination he received in service. Specifically, the Veteran has contended that at one point during his service, medical personnel came aboard his ship and were to administer a series of three shots, but after the second shot, everyone became ill and the third never was administered. See December 2013 correspondence; July 2018 Report of General Information. However, the Veteran’s service treatment records (STRs) are absent of any indication that a vaccination the Veteran received caused him to fall ill. Notably, the Veteran consistently reported “no” to experiencing any adverse reaction to a serum, drug, or medicine on his Report of Medical Histories in service. See August 1969 Report of Medical History; September 1971 Report of Medical History; and October 1973 Report of Medical History. The Board finds this contemporaneous evidence is more probative than the statements of the Veteran made decades after service. See Curry v. Brown, 7 Vet. App. 59, 68 (1994) (holding that contemporaneous records can be more probative than history as reported by a Veteran). As such, the Board does not find that a vaccination in service caused the Veteran to become ill. The Veteran also indicated in his December 2013 correspondence that he may have been exposed to unknown chemicals and biological agents when personnel from the Dugway Proving Grounds in Utah and their equipment came aboard the U.S.S. George Easton. The Veteran explained that personnel from Utah would shoot sea gulls that had been exposed during a SHAD operation and that personnel from the Veteran’s ship would retrieve the birds from the Utah personnel. See December 2013 correspondence. In his correspondence, the Veteran indicated that he did not know what types of chemicals or biological warfare agents the Utah personnel, equipment, and sea gulls may have been exposed to, but that anything they were exposed to, he contended he also was exposed to when they came aboard. The Board finds that the evidence of record is insufficient to concede exposure to any substances from the reported occurrence. There is no evidence of record, other than the Veteran’s assertion, that personnel from Utah were exposed to any chemicals or substances or that they exposed the personnel of the U.S.S. George Easton to anything if/when they came aboard. Although no development has been conducted regarding this reported incident, the Board finds the Veteran’s assertion too general and unspecific to trigger any duty to assist. In this regard, the Veteran did not provide a specific time frame during which this reported incident occurred, indicated that he was not even sure if the Utah personnel had been exposed to anything, and if they had been exposed to substances, he did not describe how he specifically was exposed to those substances when they came aboard. As such, the Board finds no development regarding such assertion was warranted. Nonetheless, in light of the Board’s concession of other in-service exposures, it finds that the second element of service connection also has been established. Turning to the third element of service connection, a nexus between the Veteran’s conditions and service, the Board finds that this element has not been established. The April 2019 Board remand includes a detailed discussion of the nature and potential health effects of the substances used in SHAD as described in a Department of Defense Fact Sheet for SHAD. Such discussion is incorporated herein by reference. The Veteran initially underwent a VA examination in July 2012 for his prostate cancer and erectile dysfunction at which time a negative etiology opinion addressing direct service connection was provided. However, in its April 2019 remand, the Board found the opinion was inadequate. As such, it is entitled to no probative weight. Pursuant to the April 2019 remand, new etiology opinions were obtained in August 2020. With regards to the Veteran’s prostate cancer, the examiner opined that the condition was less likely than not related to the Veteran’s active service, to include the conceded exposures. The examiner explained that neither the Veteran’s military occupational specialty (MOS) nor his participation in the Navy in-and-of-itself put him at greater risk of prostate cancer than the general public. He noted that regardless of any exposure to asbestos, inhaled asbestos fiber is not a risk factor for prostate cancer. He further explained that potential hazardous exposure from SHAD or otherwise are not medically like to be causative for prostate cancer. The examiner further explained that prostate cancer is the second most common cancer in men worldwide with approximately 360,000 deaths per year per the World Health Organization. He noted the most important risk factors for prostate cancer are advancing age, ethnicity, genetic factors, and dietary habits. He noted another risk factor is tobacco use, which is present in the Veteran’s past. He concluded that statistically, these risk factors in-aggregate are a more probable cause for his prostate cancer. With regards to the Veteran’s erectile dysfunction, the examiner opined that it too was less likely than not related to the Veteran’s active service, to include the conceded exposures. The examiner explained that no service, events, or exposures would likely be causative for male erectile dysfunction, and which lacks proximity to onset of erectile dysfunction by decades. The examiner also noted, albeit in his rationale for his opinion addressing secondary service-connection, that the most likely etiology of the Veteran’s erectile dysfunction is advancing age and was also postulated in the clinic note as a possible medication side effect. The Board finds these opinions, supported by rationales based on an accurate medical history with clear conclusions and supporting data, are highly probative. Nieves-Rodriguez v. Peake, 22 Vet. App. 295, 304 (2008). While the Veteran believes his prostate cancer and erectile dysfunction are related to his service, including exposure to a number of substances, he is not competent to provide a nexus opinion in this case. This issue is medically complex, as it involves internal disease processes and requires knowledge of interpretation of complicated diagnostic medical testing. Jandreau v. Nicholson, 492 F.3d 1372, 1377 n.4 (Fed. Cir. 2007). The Board also acknowledges the articles/studies submitted by the Veteran that indicate those who participated in SHAD may be at an increased risk for medical issues. The Court has held that a medical article or treatise “can provide important support when combined with an opinion of a medical professional” if the medical article or treatise evidence discusses generic relationships with a degree of certainty such that, under the facts of a specific case, there is at least “plausible causality” based upon objective facts rather than on an unsubstantiated lay medical opinion. Mattern v. West, 12 Vet. App. 222, 228 (1999); see also Sacks v. West, 11 Vet. App. 314 (1998); Wallin v. West, 11 Vet. App. 509 (1998). In short, articles, studies, and treatises tend to be general in nature and tend not to relate to the specific facts in a given veteran’s claim. In the present case, the articles/study submitted by the Veteran fall into this general category. The Board notes that the articles/study only provide general information and do not speak to this Veteran’s particular circumstances. Therefore, the Board assigns the articles no probative value in determining the nature and etiology of the Veteran’s prostate cancer and erectile dysfunction. Instead, the Board finds the August 2020 opinions more probative in determining the nature and etiology of the Veteran’s conditions as the examiner considered the specific facts of the Veteran’s claim. The Board has considered whether service connection for prostate cancer is warranted on a presumptive basis for chronic diseases. 38 C.F.R. § 3.309(a) However, the Veteran does not contend, and the evidence does not show, that he suffered from chronic prostate symptoms in and since service, that prostate cancer was diagnosed in service, or that his prostate cancer manifested to a compensable degree within a year of separation. Therefore, prostate cancer is not presumed to have been incurred in service. 38 C.F.R. § 3.309(a); Walker v. Shinseki, 708 F.3d 1331 (Fed. Cir. 2013). The Board also acknowledges that the Veteran has contended that his erectile dysfunction is secondary to his prostate cancer. However, as the Board finds service connection is not warranted for prostate cancer, it will not address this theory of entitlement. In sum, the most competent and probative evidence indicates that neither the Veteran’s prostate cancer nor erectile dysfunction are related to the conceded exposures in service. As such, service connection is not warranted. In reaching this conclusion, the Board has considered the applicability of the benefit of the doubt doctrine. However, as the preponderance of the evidence is against the Veteran’s claim, that doctrine is not applicable. See 38 U.S.C. § 5107(b); Ortiz v. Principi, 274 F.3d 1361, 1364 (Fed. Cir. 2001); Gilbert v. Derwinski, 1 Vet. App. 49, 55-57 (1990). 2. Entitlement to service connection for a respiratory disorder, to include as due to asbestos exposure, in-service duties and exposure to the chemicals, and exposures related to SHAD. The Veteran contends that his respiratory condition is related to his active military service. For the reasons that follow, the Board finds that service connection is not warranted. The Veteran’s VA treatment records show diagnoses of chronic obstructive pulmonary disease (COPD), “COPD/asthma,” bacterial bronchitis, and restrictive lung disease. Pursuant to the April 2019 remand, the Veteran underwent a VA examination for his respiratory condition in November 2019. At the examination, the examiner clarified that the Veteran’s current diagnoses include COPD and pulmonary granulomata with positive PPD. Accordingly, the first element of service connection has been established. As with the Veteran’s claim for prostate cancer and erectile dysfunction, the Veteran contends that his respiratory condition is due to a number of exposures in service, including asbestos exposure, exposures related to SHAD, and exposures related to his duties in service. As explained in detail above, these exposures have been conceded. Additionally, the Veteran’s STRs show reports of a cold and strep throat on multiple occasions as well as an upper respiratory infection. See July 1965, September 1965, December 1965, February 1967, and March 1967 STRs. Turning to the third element of service connection, a nexus, the Board finds that this element has not been established. In a July 2012 correspondence, the Veteran reported that after service he began to feel lightheaded and had trouble breathing after a short run or exertion. See also September 2018 hearing transcript. As noted above, the Veteran underwent a VA examination in November 2019 at which time an etiology opinion was obtained. The examiner opined that it was less likely than not that the Veteran’s respiratory disorders were related to the reported exposures. The examiner explained that the Veteran does not have any respiratory disorder associated with asbestos exposure, to include asbestosis and/or asbestos related benign pleural plaque, or mesothelioma. He noted that the Veteran’s pulmonary granulomata with positive PDD is due to his exposure to tuberculosis when working for the immigration service and his COPD is due to his tobacco abuse. He further explained that the Veteran’s VA Medical Center pulmonary evaluation, pulmonary function tests, and cat scan of his chest did not diagnose or identify any pulmonary condition attributed to exposure to asbestos, chemicals, or SHAD. The examiner also considered the STRs noting respiratory symptoms but opined that despite these symptoms, no chronic respiratory condition was diagnosed at any of the evaluations. The examiner also noted STRs that showed normal evaluations of the lungs and chest. In addition, while the examiner considered the Veteran’s statements regarding experiencing respiratory symptoms after service, the examiner noted that the Veteran underwent multiple evaluations for re-enlistment and served in the Reserves following his separation from active service and that none of the evaluations nor self-reporting of health identified such issues. He also noted the symptoms the Veteran reports appeared in the years following separation are non-diagnostic. The Board finds this opinion, supported by a rationale based on an accurate medical history with clear conclusions and supporting data, is highly probative. Nieves-Rodriguez, 22 Vet. App. at 304. While the Veteran believes his respiratory condition began in or is related to active service, including various exposures, he is not competent to provide a nexus opinion in this case. This issue is medically complex, as it involves internal disease processes and requires knowledge of interpretation of complicated diagnostic medical testing. Jandreau, 492 F.3d at 1377 n.4. The Board acknowledges the Veteran’s contention that his respiratory condition began in service and his reports of experiencing respiratory symptoms after service. See July 2012 correspondence; September 2018 hearing transcript. However, the VA examiner considered these reports but concluded that the Veteran’s condition was less likely than not related to his service. The Board also acknowledges the articles/studies submitted by the Veteran that indicate those who participated in SHAD may be at an increased risk for respiratory diseases. However, again, these articles/studies are general in nature and do not to relate to the specific facts of this claim. Thus, they are afforded no probative value. Rather, the Board finds the November 2019 opinion more probative in determining the nature and etiology of the Veteran’s respiratory condition as the examiner considered the specific facts of the Veteran’s claim. Based on the foregoing, service connection for a respiratory condition is not warranted. In reaching this conclusion, the Board has considered the applicability of the benefit of the doubt doctrine. However, as the preponderance of the evidence is against the Veteran’s claim, that doctrine is not applicable. See 38 U.S.C. § 5107(b); Ortiz, 274 F.3d at 1364; Gilbert, 1 Vet. App. at 55-57. 3. Entitlement to service connection for essential tremors, to include as due to asbestos exposure, in-service duties and exposure to the chemicals, and exposures related to SHAD The Veteran seeks service connection for his tremor disorder. For the reasons that follow, the Board finds that service connection is not warranted. Service connection is available for congenital diseases, but not defects, that are aggravated in service. Quirin v. Shinseki, 22 Vet. App. 390, 394 (2009); Monroe v. Brown, 4 Vet. App. 513, 515 (1993). In differentiating the two categories, a defect differs from a disease in that a defect is more or less stationary in nature, while a disease is capable of improving or deteriorating. Quirin, 22 Vet. App. at 394. Congenital or developmental defects are not diseases or injuries within the meaning of the applicable law and regulations for VA compensation purposes. 38 C.F.R. §§ 3.303(c), 4.9. However, service connection may be granted, in limited circumstances, for disability due to aggravation of a constitutional or developmental abnormality by superimposed disease or injury (see VAOPGCPREC 82-90, 55 Fed. Reg. 45,711 (1990); Carpenter v. Brown, 8 Vet. App. 240, 245 (1995); and Monroe v. Brown, 4 Vet. App. 513, 514-15 (1993)). If, during an individual’s military service, superimposed disease or injury does occur, service connection may be warranted for the resultant disability. The presumption of soundness applies to congenital diseases that are not noted at service entry. Quirin, 22 Vet. App. at 396-397. Where the presumption of soundness attaches, the burden falls on VA to rebut the presumption by clear and unmistakable evidence that the disease preexisted service and was not aggravated by service. The presumption of soundness does not attach to any period of service, including ACDUTRA, for which veteran status has not been established. VA’s Office of General Counsel also has confirmed that the existence of a congenital hereditary disease under 38 C.F.R. § 3.303(c) does not always rebut the presumption of soundness, and that service connection may be granted for congenital hereditary diseases which either first manifest themselves during service or which preexist service and progress at an abnormally high rate during service. See VAOPGCPREC 67-90; 55 Fed. Reg. 43, 253 (1990). Congenital diseases, by their very nature, preexist a claimant’s military service, and thus, the diagnosis of a congenital disease generally satisfies the first prong of rebutting the presumption of soundness. Therefore, typically, entitlement to service connection turns on the question of whether there was “aggravation” of the disease in service. See VAOPGCPREC 82-90 (noting that VA is generally justified in finding that a congenital disease, by its very nature, preexisted military service); O’Bryan v. McDonald, 771 F.3D 1376 (Fed. Cir. 2014) (indicating that diagnosis of a congenital disease satisfies the first prong of rebutting the presumption of soundness, i.e., there is clear and unmistakable evidence that the disease preexisted service). The first step in determining whether the presumption of soundness applies is to determine whether an examination was conducted at service entrance and whether the claimed condition was noted on such examination. Here, although a Report of Medical Examination was not conducted in close proximity to the Veteran’s entrance into active duty service in July 1965, a Report of Medical Examination was conducted in October 1964, and a review of his STRs indicate that this examination is considered the physical examination for his active duty service in July 1965. See July 1965 STR. A tremor disorder was not noted on the October 1964 examination. However, although no tremor disorder was noted on the Veteran’s entrance examination, the Board finds that the presumption of soundness is not applicable in this case as there was no in-service manifestation of the tremor disorder in service. The Veteran’s STRs are silent for any complaints, treatment, or diagnoses related to a tremor disorder. Additionally, the Veteran has not contended that he experienced any symptoms of his tremor disorder during his active service or that his tremor disorder began during active service. Specifically, while the Veteran has inconsistently reported when his tremors first began, which will be discussed in more detail below, he has consistently indicated that his tremors did not begin during his active service. See July 2012 correspondence (reporting onset of tremors shortly after active duty service in 1967); 2012 VA treatment records; September 2018 Board hearing (reporting onset of tremors approximately 15 to 16 years ago); November 2019 VA examination (reporting onset of tremors approximately three to four years after active duty service). Thus, without any in-service manifestation, the presumption of soundness is not for application. See Gilbert v. Shinseki, 26 Vet. App. 48, 52 (2012) (holding that absent an in-service manifestation or incurrence of a disease or injury in service, the presumption of soundness is not for application). The presumption of soundness also does not attach to any of the Veteran’s periods of ACDUTRA service as veteran status has not been established for any of those periods. Turning to whether service connection is warranted for a tremor disorder, the Board must determine whether the Veteran’s tremor disorder is a congenital disease or defect that preexisted his active service, and if so, whether such was aggravated during service. Preliminarily, the Board finds it is necessary to clarify what disorders/diagnoses it will consider in relation to the Veteran’s current claim. Pursuant to the Board’s April 2019 remand, the Veteran underwent a VA examination in November 2019. At the examination, the examiner noted diagnoses of essential tremors, also known as familial tremors, right cerebellar infarct, and vascular parkinsonism. However, the examiner indicated that the only diagnosis that was responsible for the Veteran’s tremors was his essential tremor disorder. The examiner noted that the right cerebellar infarct was not clearly symptomatic, and the Veteran’s vascular parkinsonism manifested in intermittent shuffling gait and balance impairments. The evidence of record makes clear that the Veteran is seeking service connection for his tremors. See June 2012 Statement in Support of claim; September 2018 hearing transcript. The Veteran has not reported symptoms of gait and balance impairments in connection with his claim for tremors. As the only disorder that is responsible for the Veteran’s tremors is his essential tremor disorder, and he has not indicated that he is seeking service connection for gait and balance impairments, the Board finds that right cerebellar infarct and vascular parkinsonism are not included within the scope of this appeal. Brokowski v. Shinseki, 23 Vet. App. 79 (2009); Clemons v. Shinseki, 23 Vet. App. 1, 5 (2009). Alternatively, the Board notes that the November 2019 examiner found that the Veteran did not have Parkinson’s disease and that any vascular parkinsonism was not in any way service related. With regards to the first inquiry, the Board finds that the Veteran’s essential tremor disorder is a congenital disease. VA treatment records throughout the appeal period indicate that the Veteran’s tremor disorder is familial, and a July 2012 VA examiner also indicated that the Veteran’s essential tremors are familial. In light of this evidence, the Board’s April 2019 remand requested an examiner to determine whether the Veteran’s tremor disorder was a congenital disease or defect. As noted above, the Veteran underwent a VA examination in November 2019 pursuant to the April 2019 remand. The examiner opined that the Veteran’s familial essential tremor is a genetic condition and explained that the Veteran has a documented family history of similar tremor, did not have a resting tremor or any other signs of parkinsonism on examination, and does not have Parkinson’s disease. There is no competent evidence to the contrary. Therefore, the Board finds that the Veteran’s essential tremors are a genetic condition, and therefore a congenital disease, that by its nature preexisted his military service. The Board acknowledges that the November 2019 examiner stated that while a genetic condition, the essential tremor disorder would not be considered a “congenital” condition as it did not manifest until adulthood. However, a disease is not required to manifest during childhood in order to be considered a congenital disease. The fact that a condition is genetic or of familial/hereditary origin is sufficient to place the condition under the purview of 38 C.F.R. §§ 3.303(c) and 4.9. See Chestnut v. Brown, 1997 U.S. Vet. App. LEXIS 419 (Vet. App. June 6, 1997) (noting genetic disorders fall under 38 C.F.R. § 4.9); VAOPGCPREC 82-90 (indicating that familial conditions are considered congenital conditions). Therefore, the remaining inquiry is whether the Veteran’s essential tremors were aggravated beyond their natural progression by service. As explained above, the Veteran has consistently indicated that his tremors did not begin during his active service. The November 2019 examiner opined that it was less likely than not that the Veteran’s essential tremor was aggravated beyond the natural progression during his military service. The examiner explained that it is a genetic condition that usually follows a slowly progressive course. He noted there is no evidence that the Veteran’s essential tremor, which did not become manifest until three to four years after the active service, was accelerated/aggravated during service or subsequently as a result of an in-service injury or exposure. The examiner further noted that no scientific literature regarding worsening of essential tremor by nerve gas or other potential toxic exposures the Veteran may have had was found. The Board finds this opinion highly probative as it is shown to have been based on a review of the Veteran’s record and is accompanied by a sufficient explanation. Nieves-Rodriguez, 22 Vet. App. at 304. To the extent the Veteran believes his essential tremors were aggravated during his active service, he is not competent to provide a nexus opinion in this case. This issue is medically complex, as it involves internal disease processes and requires knowledge of interpretation of complicated diagnostic medical testing. Jandreau v. Nicholson, 492 F.3d 1372, 1377 n.4 (Fed. Cir. 2007). The Board acknowledges that the Veteran has indicated that his tremors began shortly after separation from active service in 1967 as well as in 1972, a year in which he had a period of ACDUTRA. See July 2012 correspondence; 2012 VA treatment records (reporting a history of tremors for approximately 40 years). However, there is no evidence of record to indicate, and the Veteran has not contended, that his tremors initially manifested during the period of ACDUTRA, and the competent evidence of record indicates that the Veteran’s tremors were not aggravated by his military service. Additionally, the Veteran’s reports of when his tremors initially manifested have been inconsistent. See July 2012 correspondence (reporting onset of tremors shortly after active duty service in 1967); 2012 VA treatment records; September 2018 Board hearing (reporting onset of tremors approximately 15 to 16 years ago); November 2019 VA examination (reporting onset of tremors approximately three to four years after active duty service). Thus, the Board assigns limited probative weight to the Veteran’s statements regarding onset in determining whether the tremors initially manifested during a period of ACDUTRA or were aggravated by service. In sum, the most probative evidence establishes that the Veteran’s essential tremors are a congenital disease that did not initially manifest during and were not aggravated by the Veteran’s active service. The evidence in this case is not so evenly balanced so as to allow application of the benefit-of-the-doubt rule as required by law and VA regulations. 38 U.S.C. § 5107(b); 38 C.F.R. § 3.102.   The preponderance is against the Veteran’s claim, and it must be denied. C. CRAWFORD Veterans Law Judge Board of Veterans’ Appeals Attorney for the Board E. Mortimer, Associate Counsel The Board’s decision in this case is binding only with respect to the instant matter decided. This decision is not precedential and does not establish VA policies or interpretations of general applicability. 38 C.F.R. § 20.1303.