presented by Burcu Gökçe and Kemal Erdemoğlu
A 39-year-old, right-handed male presented to our outpatient clinic reporting daily occipital headache associated with recurrent syncope over a period of 2 years. His medical history was unremarkable and he took no medication on a regular basis. The patient had a normal neurological examination. His blood pressure was 120/70; his pulse rate was 70. Changes in both were physiologic when he went from supine to upright position. The patient was admitted for electroencephalogram (EEG), no epileptiform abnormalities were seen and his EEG remained normal in the later follow-ups (Figure 1). The cardiac evaluation included echocardiography, and a 24 hour Holter recording were both normal. A Doppler examination of extracranial and intracranial arteries, routine blood tests, thyroid function tests and vitamin B12 levels were also normal. Brain magnetic resonance imaging (MRI) showed a Chiari type I malformation with tonsillar herniation of 9mm below the plane of foramen magnum (Figures 2a and 2b). The patient was evaluated by neurosurgeons and decompression surgery was recommended.
Comment by the authors:
The Chiari type I malformation (CM1) is characterized by herniation of cerebellar tonsils to at least 3-5mm below the plane of foramen magnum. CM1 usually becomes symptomatic in adulthood and presents with some symptoms secondary to medullary distress, such as occipital headaches, sensorimotor abnormalities, and lower cranial nerve palsies (1). Rarely syncopal episodes have also been described (2).
Various pathophysiological mechanisms such as compression of the midbrain ascending reticular system, or vascular compromise (vertebrobasilar artery compression, hypotension secondary to cardiorespiratory center compression) have been proposed, although the exact cause of CM1 related syncope is still not well understood (3).
During a valsalva manoeuvre, intracranial pressure increases for a while and syncopes occur secondary to vertebrobasilar artery compression (4).
A certain similarity of symptoms such as dizziness, nausea, and fatigue is seen in patients with CM1, chronic fatigue syndrome, and orthostatic intolerance (OI), leading to a debate on their possible interrelation (4,5).
According to some authors orthostatic intolerance (OI) is a syndrome characterized by dizziness, nausea, and fatigue and associated with postural tachicardia (heart rate increases by at least 30 beats per minute, in upright posture) and high concentration of plasma norepinephrine concentrations (6,7).
The same condition, in the absence of specification of norepinephrine levels, is also referred to as postural orthostatic tachycardia syndrome (POTS) (5).
POTS has been defined as a rapid (within 10 minutes) increase in heart rate by more than 30 beats per minute, or to a heart rate that exceeds 120 beats per minute. People with POTS develop symptoms whenever they are in upright position (1). The pathophysiology of OI and POTS is still unknown. The blood pressure and heart rate in our patient was always within the normal range when he went from supine to upright position.
Hindbrain compression with or without CM1 can cause the symptoms of OI and it is resolved after surgical intervention but there are not many studies to prove this hypothesis (3).
Arnold-Chiari malformations should be considered in the differential diagnosis of recurrent syncope, especially if accompanied by headache, vertigo, or transient sensory or motor symptoms in arms or legs.
1. Prilipko O, Dehdashti AR, Zaim S, Seeck M. Orthostatic intolerance and syncope associated with Chiari type I malformation. J Neurol Neurosurg Psychiatry. 2005 Jul;76(7):1034-6.
2. Milhorat TH, Chou MW, Trinidad EM, et al. Chiari I malformation redefined:clinical and radiographic findings for 364 symptomatic patients.Neurosurgery 1999;44:1005–14.
3. Garland EM, Robertson D. Chiari I malformation as a cause of orthostatic intolerance symptoms: a media myth? Am J Med 2001;111:546–52.
4. Schondorf R, Freeman R. The importance of orthostatic intolerance in the chronic fatigue syndrome. Am J Med Sci 1999;317:117–23.
5. Jacob G, Biaggoni I. Idiopathic orthostatic intolerance and postural tachycardia syndromes. Am J Med Sci 1999;317:88–101.
6. Jacob G, Shannon JR, Black B, et al. Effects of volume loading and pressor agents in idiopathic orthostatic tachycardia. Circulation 1997;96:575-80.
7. Shannon JR, Flattem NL, Jordan J, Jacob G, Black BK, Biaggioni I, Blakely RD, Robertson D. Orthostatic intolerance and tachycardia associated with norepinephrine- transporter deficiency. N Engl J Med. 2000; 342: 541-9.
Burcu Gökçe and Kemal Erdemoğlu work at the Department of Neurology of Kirikkale University School of Medicine in Kirikkale, Turkey.
Comment by Pietro Cortelli
To the authors:
I agree with the short discussion that should be completed taking into account the following data:
1) A prospective study of 265 patients with Chiari malformation I (CM1) confirm that syncope is a rare phenomenon; given the definition of syncope it should be better to define these episodes as transient loss of consciousness since we are not sure that a global brain hypoperfusion is the cause (1).
2) Between the various pathophysiological mechanisms that have been proposed to explain the link between syncope and CM1 it should be underlined that the role of PoTS (postural tachycardia syndrome) as possible cause of orthostatic intolerance in CM1 (2) is only a speculation without strong supporting data.
3) A study reviewing MRI scans of the head or cervical spine from 24 female patients with orthostatic intolerance showed that the mean tonsillar depression for this group did not differ from published control values (3).
4) Please use PoTS (postural tachycardia syndrome) instead of POTS (postural and orthostatic are the same concept)
1. Mueller DM, Orò JJ. J Am Acad Nurse Pract 2005;16:134-8.
2. Prilipko O et at,. J Neurol Neuroseurg. Psychiatry 2005; 76: 1003-1036.
3. Benarroch EE. Mayo Clin Proc. 2012 Oct 31.
The authors present an interesting case that has been rarely described in the literature, but the condition is probably often unrecognized.
Various pathophysiological mechanisms have been proposed to explain the link between syncope and CM1, but still none have been demonstrated.
A) Compression of the midbrain autonomic control systems: physiologic control of blood pressure regulation involves complex afferent signal processing by the central nervous system and subsequent efferent modulation of cardiac and vascular targets. Normal regulation of arterial pressure is controlled predominantly by stretch-activated (high-pressure) baroreceptors located in the aortic arch and carotid sinus. The afferent signals are transmitted from the aortic arch by the vagus nerve and from the carotid sinus by the glossopharyngeal nerve. Phasic distension of these vascular territories after cardiac systole results in phasic discharge of afferent nerves (IX and X), which converge on the nucleus tractus solitarius (NTS) in the brainstem. This is the first relay station for these cardiovascular (but also respiratory and gastrointestinal) afferents and it’s a critical component of a variety of medullary reflexes related to all other areas of the central autonomic network. Compression of the IX and X nerves at this level (between herniated tonsils and PICA or vertebral artery) could explain the reflex syncope (neurally mediated or vasovagal). Similarly compression or ischemia of the respiratory centre in the medulla oblongata and traction upon the lower cranial nerves (especially IX or X cranial) are considered cause of respiratory disturbance in Chiari I. Beyond NTS, also compression of the intermediate reticular formation of the medulla, particularly ventrolateral medulla that controls the sympathetic and respiratory motoneurones, is considered a potential trigger area causing reflex syncope.
B) PoTS (postural tachycardia syndrome): In support of this hypothesis, Millorath reported that more than 50% of the patients with CM1 refer palpitations and more than 60 % symptoms consistent with cerebral hypoperfusion, such as light-headedness, blurred vision and cognitive difficulties. Nevertheless, PoTS is a chronic condition with no clear pathologic substrate and multiple interacting pathophysiologic mechanisms (impaired sympathetic vasoconstriction leading to venous pooling, hypovolemia, deconditioning, and hyperadrenergic state) and there is an overlap between chronic fatigue syndrome and PoTS. An MRI study of 24 female patients with orthostatic intolerance evaluated that the mean tonsillar depression for this group did not differ from published control values.
Moreover, controversy exists regarding the relationship between CM1, syncope and the benefits of decompression surgery.
In conclusion the correlation between CM1 and syncope needs to be better studied with well-controlled studies based on a more standardized approach. In these cases it is mandatory to improve the quality of diagnosis that derives from the differential diagnosis of TLoC (transient loss of consciousness) and its mimics and to perform a complete evaluation of the autonomic control of the cardiovascular system.
Pietro Cortelli is Professor of Neurology at the IRCCS Istituto delle Scienze Neurologiche di Bologna, Italy.