- Email: [email protected]
Mind the gap – Practicing neurophysiology between neurology and cardiology
Clinical Neurophysiology 127 (2016) 985–986
Contents lists available at ScienceDirect
Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph
Editorial
Mind the gap – Practicing neurophysiology between neurology and cardiology See Article, pages 1022–1030
In this issue of Clinical Neurophysiology, Saal et al. proposes an increased awareness toward the Tilt Table Test (TTT) in all neurology practices and calls on neurophysiologists and neurologists to educate themselves about how to use the test in their practice and perform the test themselves at their location of practice (Saal et al., 2016). Although primarily focused on the evaluation of the causes for transient loss of consciousness, the paper offers a comprehensive review of the physiology of the orthostatic challenge during TTT, and discusses important technical points of interest in the evaluation of patients suffering from different disorders of the nervous system. Beyond the scientific content the call from the authors also raises important questions about the organization of the diagnostic service for disorders of the autonomic nervous system. This health service planning problem differs between different settings of geography, economy and health professional training around the world. Common for all settings is the need to cover the diagnostic needs of both very frequent disorders as syncope and dizziness but also address the need of more specialized evaluation of central degenerative autonomic disorders, autonomic neuropathy and other small-fiber neuropathies. The more common disorders call on a multidisciplinary effort where cardiologist, gerontologists, as well as neurologists, must get involved in making the evaluation efficient. In this setting the TTT has a pivotal role in confirming the pathophysiological correlate of the clinical presentation. A structured clinical evaluation must ensure that patients are further evaluated in the right setting to find an etiology for the clinical problem. For this, the TTT cannot stand alone and involvement of neurologists is necessary to assure that patients with nervous system disorders are assessed further for dysfunction in the nervous system. This involvement includes establishing structured evaluation of symptoms and signs as a basis for referral to a neurologist and a neurophysiology consultation. The less frequent disorders in need of a more specialized autonomic evaluation are sometimes referred to tertiary centers from these multidisciplinary units, but more often the referral is done to confirm a diagnosis made from other symptoms or findings than syncope or orthostatic symptoms. Those tertiary centers are mostly centered in academic neuroscience centers, and as such have a heavy involvement from both neurologists and neurophysiologists.
In this more complex evaluation the TTT cannot stand alone and it should be supplemented by additional testing of autonomic function to further localize and quantify the autonomic dysfunction (England et al., 2009; Freeman and Chapleau, 2013), often resulting in complex test scores, such as the Composite Autonomic Scoring Scale (Low, 1993). This evaluation covers the cardiovascular responses to TTT, active standing and the Valsalva maneuver and tests of heart rate variability, sudomotor function and, in selected centers, examination of adrenergic function by measuring metabolites in the serum or by cardiac SPECT imaging. The examination of a skin biopsy to assess the loss of epidermal nerve fibers is especially valuable in the diagnosis of small fiber neuropathy. Most of these diagnostic tests are scientifically well-established as to their diagnostic performance in case–control studies, but their combined added-value or cost-effectiveness have generally not been evaluated in larger populations of patients with symptoms or signs of autonomic dysfunction. They remain, for now, more suited for specialized centers with scientific interest in the further development of their documentation. Although the TTT has been a widely used test in the evaluation of syncope and autonomic function for many years it is still under active investigation in select populations with orthostatic symptoms. An example of this could be the patients with orthostatic hypertension, who might be at risk of cerebrovascular events (Kario et al., 2002). As a diagnostic test TTT clearly has its shortcomings, as covered by the review, with problematic sensitivity and specificity and with a limited value in disclosing the underlying etiology of an orthostatic event. On the other hand, a TTT reproducing recognizable symptoms during a clear-cut cardiovascular episode remains a valuable diagnostic finding. The possibility of offering a non-invasive test at a potentially very low cost gives the TTT an excellent added value in the field of neurology. On this note, the review from Saal et al. is a welcome call for attention toward increased cooperation between neurosciences and other specialties to the benefit of patients with suspected autonomic nervous system dysfunction. Conflict of interest The author has no potential conflicts of interest to be disclosed.
http://dx.doi.org/10.1016/j.clinph.2015.08.017 1388-2457/Ó 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
986
Editorial / Clinical Neurophysiology 127 (2016) 985–986
References England JD, Gronseth GS, Franklin G, Carter GT, Kinsella LJ, Cohen JA, et al. Practice parameter: evaluation of distal symmetric polyneuropathy: role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review). Report of the American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation. Neurology 2009;2009(72):177–84. Freeman R, Chapleau MW. Testing the autonomic nervous system. Handb Clin Neurol 2013;115:115–36. Kario K, Eguchi K, Hoshide S, Hoshide Y, Umeda Y, Mitsuhashi T, et al. U-curve relationship between orthostatic blood pressure change and silent cerebrovascular disease in elderly hypertensives: orthostatic hypertension as a new cardiovascular risk factor. J Am Coll Cardiol 2002;40:133–41. Low PA. Composite autonomic scoring scale for laboratory quantification of generalized autonomic failure. Mayo Clin Proc 1993;68:748–52.
Saal DP, Thijs RD, van Dijk JG. Tilt table testing in neurology and clinical neurophysiology. Clin Neurophysiol 2016;127:1022–30.
⇑
Martin Ballegaard Department of Clinical Neurophysiology NF3063, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, 2100 Copenhagen, Denmark ⇑ Tel.: +45 3545 3545 E-mail address: [email protected] Available online 8 September 2015
Contents lists available at ScienceDirect
Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph
Editorial
Mind the gap – Practicing neurophysiology between neurology and cardiology See Article, pages 1022–1030
In this issue of Clinical Neurophysiology, Saal et al. proposes an increased awareness toward the Tilt Table Test (TTT) in all neurology practices and calls on neurophysiologists and neurologists to educate themselves about how to use the test in their practice and perform the test themselves at their location of practice (Saal et al., 2016). Although primarily focused on the evaluation of the causes for transient loss of consciousness, the paper offers a comprehensive review of the physiology of the orthostatic challenge during TTT, and discusses important technical points of interest in the evaluation of patients suffering from different disorders of the nervous system. Beyond the scientific content the call from the authors also raises important questions about the organization of the diagnostic service for disorders of the autonomic nervous system. This health service planning problem differs between different settings of geography, economy and health professional training around the world. Common for all settings is the need to cover the diagnostic needs of both very frequent disorders as syncope and dizziness but also address the need of more specialized evaluation of central degenerative autonomic disorders, autonomic neuropathy and other small-fiber neuropathies. The more common disorders call on a multidisciplinary effort where cardiologist, gerontologists, as well as neurologists, must get involved in making the evaluation efficient. In this setting the TTT has a pivotal role in confirming the pathophysiological correlate of the clinical presentation. A structured clinical evaluation must ensure that patients are further evaluated in the right setting to find an etiology for the clinical problem. For this, the TTT cannot stand alone and involvement of neurologists is necessary to assure that patients with nervous system disorders are assessed further for dysfunction in the nervous system. This involvement includes establishing structured evaluation of symptoms and signs as a basis for referral to a neurologist and a neurophysiology consultation. The less frequent disorders in need of a more specialized autonomic evaluation are sometimes referred to tertiary centers from these multidisciplinary units, but more often the referral is done to confirm a diagnosis made from other symptoms or findings than syncope or orthostatic symptoms. Those tertiary centers are mostly centered in academic neuroscience centers, and as such have a heavy involvement from both neurologists and neurophysiologists.
In this more complex evaluation the TTT cannot stand alone and it should be supplemented by additional testing of autonomic function to further localize and quantify the autonomic dysfunction (England et al., 2009; Freeman and Chapleau, 2013), often resulting in complex test scores, such as the Composite Autonomic Scoring Scale (Low, 1993). This evaluation covers the cardiovascular responses to TTT, active standing and the Valsalva maneuver and tests of heart rate variability, sudomotor function and, in selected centers, examination of adrenergic function by measuring metabolites in the serum or by cardiac SPECT imaging. The examination of a skin biopsy to assess the loss of epidermal nerve fibers is especially valuable in the diagnosis of small fiber neuropathy. Most of these diagnostic tests are scientifically well-established as to their diagnostic performance in case–control studies, but their combined added-value or cost-effectiveness have generally not been evaluated in larger populations of patients with symptoms or signs of autonomic dysfunction. They remain, for now, more suited for specialized centers with scientific interest in the further development of their documentation. Although the TTT has been a widely used test in the evaluation of syncope and autonomic function for many years it is still under active investigation in select populations with orthostatic symptoms. An example of this could be the patients with orthostatic hypertension, who might be at risk of cerebrovascular events (Kario et al., 2002). As a diagnostic test TTT clearly has its shortcomings, as covered by the review, with problematic sensitivity and specificity and with a limited value in disclosing the underlying etiology of an orthostatic event. On the other hand, a TTT reproducing recognizable symptoms during a clear-cut cardiovascular episode remains a valuable diagnostic finding. The possibility of offering a non-invasive test at a potentially very low cost gives the TTT an excellent added value in the field of neurology. On this note, the review from Saal et al. is a welcome call for attention toward increased cooperation between neurosciences and other specialties to the benefit of patients with suspected autonomic nervous system dysfunction. Conflict of interest The author has no potential conflicts of interest to be disclosed.
http://dx.doi.org/10.1016/j.clinph.2015.08.017 1388-2457/Ó 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
986
Editorial / Clinical Neurophysiology 127 (2016) 985–986
References England JD, Gronseth GS, Franklin G, Carter GT, Kinsella LJ, Cohen JA, et al. Practice parameter: evaluation of distal symmetric polyneuropathy: role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review). Report of the American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation. Neurology 2009;2009(72):177–84. Freeman R, Chapleau MW. Testing the autonomic nervous system. Handb Clin Neurol 2013;115:115–36. Kario K, Eguchi K, Hoshide S, Hoshide Y, Umeda Y, Mitsuhashi T, et al. U-curve relationship between orthostatic blood pressure change and silent cerebrovascular disease in elderly hypertensives: orthostatic hypertension as a new cardiovascular risk factor. J Am Coll Cardiol 2002;40:133–41. Low PA. Composite autonomic scoring scale for laboratory quantification of generalized autonomic failure. Mayo Clin Proc 1993;68:748–52.
Saal DP, Thijs RD, van Dijk JG. Tilt table testing in neurology and clinical neurophysiology. Clin Neurophysiol 2016;127:1022–30.
⇑
Martin Ballegaard Department of Clinical Neurophysiology NF3063, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, 2100 Copenhagen, Denmark ⇑ Tel.: +45 3545 3545 E-mail address: [email protected] Available online 8 September 2015