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August 1, 2017 Circulation. 2017;136:e60–e122. DOI: 10.1161/CIR.0000000000000499 e76

3.3 Neurological Testing: Recommendations

3.3.1 Autonomic Evaluation: Recommendation

Syncope due to neurogenic OH is common in patients with central or peripheral autonomic nervous system damage or dysfunction. Its causes should be sought so as to provide efficient, accurate, and effective management. Some symptoms of neurogenic OH may differ from those due to dehydration, drugs, and cardiac and reflex syncope; these include persistent and often progressive generalized weakness, fatigue, visual blurring, cognitive slowing, leg buckling, and the “coat hanger” headache (a triangular headache at the base of the neck due to trapezius ischemia). These symptoms may be provoked or exacerbated by exertion, prolonged standing, meals, or increased ambient temperature. Confirmation of specific neurogenic OH conditions causing syncope often requires additional autonomic evaluation.

Table 7.  Examples of Serious Medical Conditions That Might Warrant Consideration of Further Evaluation and Therapy in a Hospital Setting

Cardiac Arrhythmic Conditions Cardiac or Vascular Nonarrhythmic Conditions Noncardiac Conditions Sustained or symptomatic VT Symptomatic conduction system disease or Mobitz II or third-degree heart block Symptomatic bradycardia or sinus pauses not related to neurally mediated syncope Symptomatic SVT Pacemaker/ICD malfunction Inheritable cardiovascular conditions predisposing to arrhythmias Cardiac ischemia

Severe aortic stenosis Cardiac tamponade HCM Severe prosthetic valve dysfunction Pulmonary embolism Aortic dissection Acute HF Moderate-to-severe LV dysfunction Severe anemia/gastrointestinal bleeding

Major traumatic injury due to syncope Persistent vital sign abnormalities

HCM indicates hypertrophic cardiomyopathy; HF, heart failure; ICD, implantable cardioverter-defibrillator; LV, left ventricular; SVT, supraventricular tachycardia; and VT, ventricular tachycardia.

Recommendation for Autonomic Evaluation

COR LOE Recommendation IIa C-LD Referral for autonomic evaluation can be useful to improve diagnostic and prognostic accuracy in selected patients with syncope and known or suspected neurodegenerative disease.219,236–239

See Online Data Supplement 16. The care of patients with neurogenic OH is complex, especially in individuals with neurodegenerative disease. Care providers must be knowledgeable in the pathophysiology of the autonomic nervous system and the pharmacology of treatments for neurodegenerative disease.33,240 Many symptomatic treatments for neurodegenerative disease will increase the risk of syncope due to worsening OH; selection of these treatments needs to be balanced against the increased morbidity of not treating the symptoms of the neurodegenerative disease. Such care may be provided by a neurologist, cardiologist, internist, or other physician who has sufficient training to treat these complicated patients.

Syncope due to neurogenic OH is caused by either central or peripheral autonomic nervous system damage or dysfunction. Central autonomic degenerative disorders include multiple system atrophy,241 Parkinson’s disease,242 and Lewy Body dementia.238 Peripheral autonomic dysfunction may be due to a selective degeneration of peripheral autonomic neurons, known as pure autonomic failure,243 or may accompany autonomic peripheral neuropathies, such as neuropathies due to diabetes amyloidosis, immune-mediated neuropathies, hereditary sensory and autonomic neuropathies, and inflammatory neuropathies. Peripheral neuropathies due to vitamin B12 deficiency, neurotoxic exposure, HIV and other infections, and porphyria are less common causes of neurogenic OH.240 It can be useful to consider referring patients with the following characteristics for autonomic evaluation: Parkinsonism241,244–246 or other central nervous system features,247,248 peripheral neuropathies,240 underlying diseases known to be associated with a peripheral neuropathy,240,248 progressive autonomic dysfunction without central or peripheral nervous system features,243,248 postprandial hypotension,248,249 and known or suspected neuropathic postural tachycardia syndrome (POTS).37,248,250 Autonomic evaluation may: 1) determine the underlying cause of neurogenic OH; 2) provide prognostic information; and 3) have therapeutic implications.

3.3.2. Neurological and Imaging Diagnostics: Recommendations Many patients undergo extensive neurological investigation after an uncomplicated syncope event, despite the absence of neurological features on history or examination. A systematic review found that EEG, CT, MRI, and carotid ultrasound were ordered in 11% to 58% of patients with a presentation of syncope.78 The evidence suggests that routine neurological testing is of very limited value in the context of syncope evaluation and management; the diagnostic yield is low, with very high cost per diagnosis.36,77,78,251–260 The recommendations pertain to the use of these investigations in patients with syncope and not in patients in the wider category of transient loss of consciousness.

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