Citation Nr: 21030398 Decision Date: 05/18/21 Archive Date: 05/18/21 DOCKET NO. 16-06 966 DATE: May 18, 2021 ORDER Entitlement to an initial evaluation in excess of 60 percent for coronary artery disease is denied. Entitlement to an evaluation in excess of 20 percent for diabetes mellitus is denied. REMANDED Entitlement to compensation for a left hip disability, to include compensation under 38 U.S.C. § 1151 for residuals of an intraoperative fracture of the proximal left femur, is remanded. Entitlement to service connection for sleep apnea, claimed as secondary to a service-connected acquired psychiatric disability, is remanded. Entitlement to service connection for headaches, to include as due to service-connected disabilities, is remanded. Entitlement to a total disability rating based upon individual unemployability due to service-connected disabilities (TDIU) prior to October 26, 2016, is remanded. FINDINGS OF FACT 1. The Veteran has not been shown to have chronic congestive heart failure; a workload of 3 METs or less resulting in dyspnea, fatigue, angina, dizziness, or syncope; or, left ventricular dysfunction with an ejection fraction of less than 30 percent. 2. The Veteran's service-connected diabetes mellitus requires a restricted diet, an oral hypoglycemic agent, and insulin, but does not require a regulation of activities. CONCLUSIONS OF LAW 1. The criteria for an initial evaluation in excess of 60 percent for coronary artery disease have not been met. 38 U.S.C. § 1155; 38 C.F.R. §§ 3.102, 4.1-4.14, 4.100, 4.104, Diagnostic Code 7005. 2. The criteria for an evaluation in excess of 20 percent for diabetes mellitus have not been met. 38 U.S.C. § 1155; 38 C.F.R. §§ 3.102, 3.159, 4.1-4.14, 4.119, Diagnostic Code 7913. REASONS AND BASES FOR FINDINGS AND CONCLUSIONS The Veteran served on active duty in the United States Army from September 1967 to October 1978, to include service in Vietnam. His decorations include the Combat Infantryman Badge and the Purple Heart. This case comes before the Board of Veterans' Appeals (Board) on merged appeals from rating decisions by the Department of Veterans Affairs (VA) Regional Office (RO). The Board remanded the case for further development in September 2018, August 2019, April 2020 and June 2020. That development was completed, and the case has since been returned to the Board for appellate review. A September 2020 rating decision granted TDIU, effective from October 26, 2016. The matter of entitlement to TDIU prior to October 26, 2016, remains before the Board. See Payne v. Wilkie, 31 Vet. App. 373 (2019); Harper v. Wilkie, 30 Vet. App. 356 (2018). Law and Analysis Disability ratings are determined by applying the criteria set forth in the VA Schedule for Rating Disabilities, found in 38 C.F.R., Part 4. The rating schedule is primarily a guide in the evaluation of disability resulting from all types of diseases and injuries encountered as a result of or incident to military service. The ratings are intended to compensate, as far as can practicably be determined, the average impairment of earning capacity resulting from such diseases and injuries and their residual conditions in civilian occupations. 38 U.S.C. § 1155; 38 C.F.R. § 4.1. Where there is a question as to which of two evaluations shall be applied, the higher evaluation will be assigned if the disability picture more nearly approximates the criteria for that rating. 38 C.F.R. § 4.7. In considering the severity of a disability, it is essential to trace the medical history of the veteran. 38 C.F.R. §§ 4.1, 4.2, 4.41. Consideration of the whole-recorded history is necessary so that a rating may accurately reflect the elements of disability present. 38 C.F.R. § 4.2; Peyton v. Derwinski, 1 Vet. App. 282 (1991). While the regulations require review of the recorded history of a disability by the adjudicator to ensure a more accurate evaluation, the regulations do not give past medical reports precedence over the current medical findings. Where entitlement to compensation has already been established and an increase in the disability rating is at issue, it is the present level of disability that is of primary concern. Francisco v. Brown, 7 Vet. App. 55, 58 (1994). However, where the question for consideration is the propriety of the initial rating assigned, evaluation of the evidence since the effective date of the grant of service connection is required. Fenderson v. West, 12 Vet. App. 119, 125-26 (1999). Where VA's adjudication of the claim for increase is lengthy and factual findings show distinct time periods where the service-connected disability exhibits symptoms which would warrant different ratings, different or "staged" ratings may be assigned for such different periods of time. Hart v. Mansfield, 21 Vet. App. 505, 509-10 (2007); Fenderson, 12 Vet. App. at 126-27. Except as otherwise provided by law, a claimant has the responsibility to present and support a claim for benefits. VA shall consider all information and lay and medical evidence of record in a case and when there is an approximate balance of positive and negative evidence regarding any issue material to the determination of a matter, VA shall give the benefit of the doubt to the claimant. 38 U.S.C. § 5107; 38 C.F.R. § 3.102; Gilbert v. Derwinski, 1 Vet. App. 49, 53 (1990). To deny a claim on its merits, the weight of the evidence must be against the claim. Alemany v. Brown, 9 Vet. App. 518, 519 (1996). 1. Entitlement to an initial evaluation in excess of 60 percent disabling for coronary artery disease (CAD) is denied In this case, the Veteran's service-connected coronary artery disease is currently assigned a 60 percent evaluation pursuant to 38 C.F.R. § 4.104, Diagnostic Code 7005. A 60 percent evaluation is warranted where there is evidence of more than one episode of acute congestive heart failure in the past year; or, workload of greater than 3 METs but not greater than 5 METs resulting in dyspnea, fatigue, angina, dizziness, or syncope; or left ventricular dysfunction with an ejection fraction of 30 to 50 percent. A 100 percent evaluation is warranted where there is chronic congestive heart failure; or workload of 3 METs or less resulting in dyspnea, fatigue, angina, dizziness or syncope; or, left ventricular dysfunction with an ejection fraction of less than 30 percent. When evaluating disabilities of the cardiovascular system under Diagnostic Codes 7000-7007, 7011, and 7015-7020, it must be ascertained in all cases whether or not cardiac hypertrophy or dilatation (documented by electrocardiogram, echocardiogram, or x-ray) is present and whether or not there is a need for continuous medication. METs testing is required in all cases except: (1) when there is a medical contraindication; (2) when the left ventricular ejection fraction (LVEF) has been measured and is 50 percent or less; (3) when chronic congestive heart failure is present or there has been more than one episode of congestive heart failure within the past year; (4) when a 100 percent evaluation can be assigned on another basis. If LVEF testing is not of record, evaluate based on the alternative criteria unless the examiner states that the LVEF test is needed in a particular case because the available medical information does not sufficiently reflect the severity of the veteran's cardiovascular disability. 38 C.F.R. § 4.100(a)-(c). One MET is the energy cost of standing quietly at rest and represents an oxygen uptake of 3.5 milliliters per kilogram of body weight per minute. When the level of METs at which dyspnea, fatigue, angina, dizziness, or syncope develops is required for evaluation, and a laboratory determination of METs by exercise testing cannot be done for medical reasons, an estimation by a medical examiner of the level of activity (expressed in METs and supported by specific examples, such as slow stair climbing or shoveling snow) that results in dyspnea, fatigue, angina, dizziness, or syncope may be used. 38 C.F.R. § 4.104, Note (2). In considering the evidence of record under the laws and regulations as set forth above, the Board concludes that the Veteran is not entitled to an initial evaluation in excess of 60 percent for his service-connected coronary artery disease. The Veteran was afforded a VA examination in connection with the claim for service connection for CAD in July 2018. The examiner noted the diagnosis of left ventricular hypertrophy with diastolic dysfunction and the Veteran's complaints of shortness of breath with physical activity. He did not require continuous medication for the heart condition. He did not have congestive heart failure. Cardiac hypertrophy was found on echocardiogram. There was no evidence of cardiac dilatation. Left ventricular ejection fraction (LVEF) was measured as 45-50 percent. Exercise stress testing was not performed as it was not required as part of his current treatment plan and the test was not without significant risk. An interview-based METs test indicated dyspnea at greater than 3-5 METs, consistent with activities such as light yard work (weeding), mowing the lawn with a power mower or brisk walking (4 mph). Functional impact was described as difficulty performing physically demanding jobs. See July 2018 VA examination report. Another VA examination was performed in June 2019. At that time, the Veteran reported chest pain and dyspnea, worse with exertion. He also reported difficulty with physically strenuous activity. Medications at that time included aspirin, Plavix, Atenolol, lisinopril, and Crestor. He did not have congestive heart failure. The examiner noted evidence of cardiac hypertrophy on the July 2018 echocardiogram. There was no evidence of cardiac dilatation. Chest x-rays were normal. The July 2018 echocardiogram showed LVEF of 45-50 percent with borderline left ventricular hypertrophy. An interview-based METs test indicated symptoms of dyspnea and angina at greater than 3-5 METs, consistent with activities such as light yard work, mowing the lawn with a power mower, and brisk walking. Functional impact was described as difficulty with high-stress level jobs and physically strenuous jobs. See June 2019 VA examination report. The evidence of record does not show that the Veteran has chronic congestive heart failure. In fact, the July 2018 and June 2019 VA examiners found that he does not have congestive heart failure. The evidence of record also does not show that the Veteran has a workload of 3 METs or less resulting in dyspnea, fatigue, angina, dizziness, or syncope. In addition, the Veteran has not been shown to have ventricular dysfunction with an ejection fraction of less than 30 percent. Based on the foregoing, the Board finds that the weight of the evidence is against the Veteran's claim. As such, the benefit-of-the-doubt rule does not apply, and the claim is denied. Gilbert, 1 Vet. App. 49 (1990). 2. Entitlement to an evaluation in excess of 20 percent for diabetes mellitus is denied In this case, the Veteran's service-connected diabetes mellitus is currently assigned a 20 percent evaluation pursuant to 38 C.F.R. § 4.119, Diagnostic Code 7913. Under that diagnostic code, a 20 percent disability evaluation is assigned for diabetes mellitus requiring insulin and restricted diet; or, an oral hypoglycemic agent and restricted diet. A 40 percent disability evaluation is contemplated for diabetes mellitus requiring insulin, restricted diet, and regulation of activities. A 60 percent disability evaluation is warranted for diabetes mellitus requiring insulin, a restricted diet, and regulation of activities, with episodes of ketoacidosis or hypoglycemic reactions requiring one or two hospitalizations per year or twice a month visits to a diabetic care provider, plus complications that would not be compensable if separately evaluated. A 100 percent evaluation is contemplated for diabetes mellitus requiring more than one daily injection of insulin, restricted diet, and regulation of activities (avoidance of strenuous occupational and recreational activities) with episodes of ketoacidosis or hypoglycemic reactions requiring at least three hospitalizations per year or weekly visits to a diabetic care provider, plus progressive loss of weight and strength or complications that would be compensable if separately evaluated. The Court has held that, in order to demonstrate a regulation of activities, "medical evidence" is required to show that both occupational and recreational activities have been restricted. Camacho v. Nicholson, 21 Vet. App. 360, 364 (2007). The phrase "regulation of activities" means "avoidance of strenuous occupational and recreational activities." Camacho, 21 Vet. App. at 362 (quoting 38 C.F.R. § 4.119, Diagnostic Code 7913 (defining the term within the criteria for a 100 percent rating)). Successive rating criteria, such as Diagnostic Code 7913, is where the evaluation for each higher disability rating includes the criteria of each lower disability rating, such that if a component is not met at any one level, the veteran can only be rated at the level that does not require the missing component. Tatum v. Shinseki, 23 Vet. App. 152, 156 (2009). For example, the diagnostic code for diabetes mellitus (Diagnostic Code 7913) is successive because each higher evaluation requires the elements of the lower evaluation: the 10 percent evaluation requires a restricted diet; the 20 percent evaluation requires a restricted diet and insulin or oral hypoglycemic agent, the 40 percent evaluation requires insulin, restricted diet, and regulation of activities; and so forth. Camacho, 21 Vet. App. at 366. In considering the evidence of record under the laws and regulations as set forth above, the Board concludes that the Veteran is not entitled to an increased evaluation for his service-connected diabetes mellitus. The evidence of record establishes that the Veteran's diabetes mellitus requires an oral hypoglycemic agent and a restricted diet, but not a regulation of his activities. The evidence also establishes that this has been consistent over the entire period of appeal, thus any "staged" ratings would be unwarranted. The Veteran filed his claim for an increased rating for Type II diabetes mellitus in June 2016 and was afforded a VA examination in July 2016. The examiner noted that he was prescribed an oral hypoglycemic agent and required more than one insulin injection per day. However, he did not require regulation of activities as part of medical management of diabetes mellitus. The Veteran described the functional impact of his diabetes as "inconsistent, I may be doing something and I start to feel bad and check sugars and eat something." See July 2016 VA examination report. A June 2017 treatment note indicated that he was instructed to walk 40 minutes or more daily as tolerated and combine aerobic exercises with weightlifting. In June 2018, it was noted that he was not physically active due to hip replacements and back pain, but he planned to get a stationary bike from his sister to see if he could tolerate it. He was instructed on the importance of physical activity to control his diabetes. Another VA examination in connection with the claim for an increased rating for diabetes mellitus was performed in December 2019. The examiner indicated that his diabetes was managed by a restricted diet and oral hypoglycemic agents and required one insulin injection per day. However, he did not require regulation of his activities as part of medical management of diabetes mellitus. Complications included diabetic peripheral neuropathy and erectile dysfunction, which are separately evaluated. There was no functional impact attributable to diabetes reported or identified by the examiner. See December 2019 VA examination report. The Board finds that the Veteran is not required to regulate his activities for the management of his diabetes mellitus. As noted above, an evaluation of 40 percent requires insulin, a restricted diet, and regulation of activities. 38 C.F.R. § 4.119, Diagnostic Code 7913. Accordingly, an evaluation in excess of 20 percent is not warranted. In rendering this decision, the Board has also considered the lay evidence of record, to include his assertion that he is experiencing "low activity levels" due to his diabetes. See June 2016 statement in support of claim. As noted above, medical evidence is required to show that both occupational and recreational activities have been restricted. Camacho v. Nicholson, 21 Vet. App. 360, 364 (2007). There is no medical evidence of regulation of activities; to the contrary, the treatment records indicate that he was encouraged to exercise. Therefore, the Veteran's lay statements do not support a finding that an increased evaluation is warranted. The Board also acknowledges that the Veteran has diabetic peripheral neuropathy; however, the Veteran has already been granted service connection for that disability and is assigned separate ratings, which contemplate symptoms resulting from that condition. Similarly, the Veteran has been granted service connection for erectile dysfunction associated with his diabetes mellitus. There is no evidence of any other service-connected diabetic complications. Indeed, the evidence of record does not show any other pertinent physical findings, complications, conditions, signs, or symptoms related to the Veteran's service-connected diabetes mellitus. Based upon the evidence of record, the Veteran has not been shown to meet the criteria for an increased evaluation under the rating criteria. Accordingly, the Veteran is not entitled to an evaluation in excess of 20 percent for his service-connected diabetes mellitus. REASONS FOR REMAND 1. Entitlement to compensation for a left hip disability, to include compensation under 38 U.S.C. § 1151 for residuals of an intraoperative fracture of the proximal left femur, is remanded. Although the Board sincerely regrets further delay, remand is necessary to ensure proper adjudication. On remand, the examiner was requested to address whether the Veteran has any additional disability as the result of VA medical treatment, and whether such disability was the result of carelessness, negligence, lack of proper skill, error in judgment, or similar instance of fault on the part of VA, or whether such disability was the result of an event not reasonably foreseeable. In the July 2020 VA medical opinion, the examiner opined that the claimed disability of sciatic nerve damage on the left side was at least as likely as not caused by the 2004 left hip total arthroplasty. The examiner explained that intraoperative injury to the sciatic nerve is a known risk during total hip replacement and, although not deliberate, the nerve can be injured trying to gain better exposure to the hip joint. The examiner found no evidence of carelessness, negligence, lack of skill, or similar incidence of fault on the part of attending VA personnel. However, the opinion is conflicting with regard to whether intraoperative injury to the sciatic nerve was an event not reasonably foreseeable. The examiner stated that "it would be speculative" to say that the sciatic nerve damage resulted from an event that could not have reasonably been foreseen by a reasonable healthcare provider. He also stated that, in his opinion, the event could not have been foreseen. Elsewhere in the opinion, however, the examiner stated that intraoperative injury to the sciatic nerve is a "known risk" during total hip replacement. See July 2020 VA medical opinion. An October 2020 addendum opinion did not contain sufficient rationale. Therefore, it is necessary to remand for a clarifying VA medical opinion. 2. Entitlement to service connection for sleep apnea, claimed as secondary to service-connected acquired psychiatric disability, is remanded. This issue was previously remanded in April 2020 for a VA examination. It was noted that the Veteran had a diagnosis of obstructive sleep apnea following a sleep study in January 2017 and was prescribed a continuous positive airway pressure (CPAP) device. In addition, he submitted an April 2019 private medical opinion from Dr. H.S. (initials used to protect privacy), discussing the comorbidity of sleep apnea and psychiatric disorders including depression. See April 2020 Board decision. A VA medical opinion was obtained in July 2020. The examiner noted the diagnosis of obstructive sleep apnea in January 2017. The examiner opined that his sleep apnea is less likely than not related to active service, explaining that although he complained of insomnia in June 1978, insomnia is not a sign of sleep apnea and the two are mutually exclusive. Insomnia is a sleep disorder in which people have trouble sleeping, whereas people with sleep apnea have no trouble falling or staying asleep. Review of the service treatment records showed no evidence of diagnosis or treatment for sleep apnea or diagnostic polysomnography during active duty service. In addition, symptoms including snoring, unrestful sleep, and shallow breathing are not pathognomonic for sleep apnea. See July 2020 VA examination report. The examiner also opined that the Veteran's sleep apnea is less likely than not proximately due to or the result of his service-connected acquired psychiatric disability. The examiner explained that obstructive sleep apnea is due to upper airway soft tissue abnormalities/obesity and the medical literature does not support a mental health condition (to include acquired psychiatric disorder, major depressive disorder with anxious distress, alcohol use disorder) as causative or the potential for aggravation of the physiologic condition of obstructive sleep apnea. See July 2020 VA examination report. Nevertheless, the July 2020 examiner did not specifically address the April 2019 private DBQ from Dr. H.S., including his statement that psychiatric disorders are commonly associated with obstructive sleep apnea. Dr. H.S. cited studies finding that obstructive sleep apnea and psychiatric disorders including depression are comorbid conditions and opined that the Veteran's psychiatric disability has aggravated his obstructive sleep apnea. Nor did the VA examiner consider the medical research articles submitted by the Veteran regarding the association between psychiatric disorders and sleep apnea. See February 2020 third-party correspondence. Therefore, the Board finds that an additional medical opinion is needed. 3. Entitlement to service connection for headaches, to include as due to service-connected disabilities, is remanded. The service treatment records document complaints of chronic headaches since age 10, when he fell on his head. See November 1976 report of medical history. See also July 1978 report of medical history (reporting past or present frequent or severe headaches which occur constantly). In support of the negative nexus opinion, the May 2020 examiner stated that the Veteran's post-discharge medical records are negative for complaints, diagnosis or treatment related to migraine headaches, with the only mention of headaches being that of a prior history of migraines which resolved in 1968. However, while the Veteran reported that his last episode of migraine headaches was in 1968, he continued to complain of chronic headaches after service. See, e.g., February 2002, May 2011, May 2016 VA treatment records. See Reonal v. Brown, 5 Vet. App. 458, 461 (1993) (holding that a medical opinion based upon an incomplete or inaccurate factual premise has no probative value). The examiner opined that the Veteran's claimed migraine headaches were less likely than not caused or aggravated by service-connected acquired psychiatric disability and/or tinnitus, explaining that there is no clinical indication in the records of any causal relationship between these conditions. However, the examiner failed to specifically address the evidence submitted by the Veteran, including the April 2019 private DBQ and medical opinion submitted by Dr. H.S. on the Veteran's behalf, opining that his service-connected tinnitus and major depressive disorder with anxious distress aggravate his headaches. The Veteran also submitted a medical research article regarding the relationship between migraine headaches and depression. See March 2020 correspondence. It is necessary to remand for the examiner to specifically discuss this evidence. Moreover, the examiner stated that his migraine headaches clearly and unmistakably preexisted service and were not aggravated beyond the natural progression by his service-connected acquired psychiatric disability and/or tinnitus. See May 2020 VA examination report. If there is a preexisting disorder, the question is whether there is clear and unmistakable evidence showing that a preexisting disorder was not aggravated by service, as opposed to whether there is sufficient evidence showing aggravation. The examiner's opinion is inadequate because it employs the incorrect standard regarding preexisting headaches and does not provide sufficient rationale as to why the Veteran's headaches were not aggravated by service and/or his service-connected acquired psychiatric disability and tinnitus. Thus, because the May 2020 examiner's opinion is inadequate, an addendum opinion must be obtained on remand. In addition, on remand, the examiner should address the Veteran's assertions that medications for his service-connected erectile dysfunction and heart disability, including Viagra and nitroglycerin, aggravate his headaches. See September 2000, July 2003 VA treatment records. 4. Entitlement to a TDIU prior to October 26, 2016, is remanded. The issue of entitlement to TDIU is inextricably intertwined with the other claims being remanded. Harris v. Derwinski, 1 Vet. App. 180, 183 (1991) (noting that two issues are inextricably intertwined when the adjudication of one issue could have significant impact on the other issue). The appropriate remedy where a pending claim is inextricably intertwined with a claim currently on appeal is to remand the claim on appeal pending adjudication. For the above reasons, the TDIU claim is remanded. The matters are REMANDED for the following action: 1. Obtain copies of records pertaining to any VA treatment the Veteran has received since the time that such records were last procured, following the procedures set forth in 38 C.F.R. § 3.159. The evidence obtained, if any, should be associated with the record. 2. Schedule the Veteran for an examination by an appropriate clinician to determine whether the Veteran has any additional disability as the result of VA medical treatment, and whether such disability was the result of carelessness, negligence, lack of proper skill, error in judgment, or similar instance of fault on the part of VA, or whether such disability was the result of an event not reasonably foreseeable. The examiner must opine as to the following: (a) Whether it is at least as likely as not that any additional disability was either caused or accelerated beyond its natural progression by VA medical treatment, including from the November 2004 left hip arthroplasty. (b) If it is at least as likely as not that the Veteran incurred additional disability as a result of any VA medical treatment, including from the November 2004 left hip arthroplasty, the VA examiner should also opine, in regard to each disability identified, as to whether the proximate cause of such disability was (i) carelessness, negligence, lack of proper skill, error in judgment, or a similar instance of fault on the part of VA; or (ii) an event not reasonably foreseeable. (c) In determining whether any additional disability was the result of carelessness, negligence, lack of proper skill, error in judgment, or a similar instance of fault on the part of VA, the examiner should specifically consider whether VA failed to exercise the degree of care that would be expected of a reasonable health care provider. (d) The examiner is advised that, whether the proximate (i.e., direct) cause of a Veteran's additional disability was an event not reasonably foreseeable is to be determined based on what a reasonable health care provider would have foreseen. The event need not be completely unforeseeable or unimaginable but must be one that a reasonable health care provider would not have considered to be an ordinary risk of the treatment provided. In responding to these questions, the examiner must consider and address whether the procedure in question caused additional disability relative to sciatic nerve damage, burning and loss of sensation in the left calf and foot, worsened left hip pain, left hip locking, recurrent left hip dislocation, cramping, popping, and slipping. The examiner should provide a complete rationale for all opinions expressed. 3. After completing the foregoing development, the AOJ should refer the Veteran's claims file to a suitably qualified VA examiner for a medical opinion as to the nature and etiology of his sleep apnea. A physical examination is only needed if deemed necessary by the VA examiner. The examiner is requested to review all pertinent records associated with the claims file, including the Veteran's service treatment records, post-service medical records, and assertions. The examiner should note that the Veteran is competent to attest to factual matters of which he has first-hand knowledge. If there is a medical basis to support or doubt the history provided by the Veteran, the examiner should state this with a fully reasoned explanation. The examiner should state whether it is at least as likely as not that the Veteran's sleep apnea manifested in service or is otherwise causally or etiologically related to the Veteran's military service, to include any symptomatology therein. The examiner should also provide an opinion as to whether it is at least as likely as not that the Veteran's obstructive sleep apnea was either caused by or aggravated by his service-connected acquired psychiatric disorder, to include major depressive disorder with anxious distress features and alcohol use disorder. In rendering his or her opinion, the examiner should address both the causation and aggravation questions in his or her rationale. In other words, even if the Veteran's psychiatric disability did not cause his current sleep apnea, the examiner should still address whether his psychiatric disability could have worsened his sleep apnea. In rendering his or her opinions, the examiner should consider the April 2019 medical opinion from Dr. H.S. and the research studies submitted on the Veteran's behalf. See February 2020 third-party correspondence. (The term "at least as likely as not" does not mean within the realm of medical possibility, but rather that the medical evidence both for and against a conclusion is so evenly divided that it is as medically sound to find in favor of the conclusion as it is to find against it.) A clear rationale for all opinions must be provided, and a discussion of the facts and medical principles involved would be of considerable assistance to the Board. 4. After completing the foregoing development, the Veteran should be afforded a VA examination to determine the nature and etiology of any headache disorder that may be present. Any and all studies, tests, and evaluations deemed necessary by the examiner should be performed. The examiner is requested to review all pertinent records associated with the claims file, including the service treatment records, post-service medical records, and lay statements. It should be noted that the Veteran is competent to attest to matters of which he has first-hand knowledge, including observable symptomatology. If there is a clinical basis to support or doubt the history provided by the Veteran, the examiner should provide a fully reasoned explanation. The examiner should opine as to whether any current headache disorder clearly and unmistakably preexisted his military service. (The term "clear and unmistakable" means that the evidence is undebatable.) If the disorder did clearly and unmistakably preexist service, the examiner should state whether there was an increase in the severity of the preexisting disorder during this period of service and whether any increase was due to the natural progression of the disorder or whether it represented a chronic worsening of the underlying pathology. If the examiner determines that the disorder did not clearly and unmistakably preexist the Veteran's service, he or she should provide an opinion as to whether it is at least as likely as not that the Veteran's current headache disorder manifested in service or is otherwise causally or etiologically related to his military service, to include any injury and symptomatology therein. The examiner should also opine as to whether it is at least as likely as not that the Veteran has a headache disorder that is either caused or aggravated by his service-connected acquired psychiatric disability and/or tinnitus or any medication that has been prescribed for his service-connected disabilities including coronary artery disease and erectile dysfunction. The examiner should specifically discuss the April 2019 DBQ by Dr. H.S. and the medical research submitted by the Veteran. See March 2020 correspondence. (The term "at least as likely as not" does not mean within the realm of medical possibility, but rather that the medical evidence both for and against a conclusion is so evenly divided that it is as medically sound to find in favor of the conclusion as it is to find against it.) A clear rationale for all opinions would be helpful, and a discussion of the facts and medical principles involved would be of considerable assistance to the Board. 5. Thereafter, readjudicate the issues on appeal, including TDIU prior to October 26, 2016. James Springer Acting Veterans Law Judge Board of Veterans' Appeals Attorney for the Board D.S. Chilcote, 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.