Dr. Oro is a neurosurgeon who specializes in treatment of Chiari malformation. Actually, he's the Medical Director of Neurosurgery at The Medical Center of Aurora in Aurora, Colorado. He's been reviewing the various clinical presentations of Chiari malformation on his blog. Here is a recent posting in this series, on the presenting symptom of syncope.
MRI of a teenage girl with headache, fatigue, double vision, dizziness and blackout spells. The cerebellar tonsils (T) are herniated into the upper cervical canal, the brainstem (B) is elongated, and the odontoid process of C2 is distorting the anterior surface of the medulla.
Recent posts reviewed cerebellar fits, neurally mediated syncope, and breath-holding spells. Today, we look at syncope in persons with the Chiari I malformation (CM-I).
A PubMed search for “Chiari syncope” reveals 31 reports, although the abstracts are not available for each. The earliest report listed, ‘Sneeze syncope’, basilar invagination, and Arnold-Chiari type 1 malformation, was published by Corbett et al. in 1976. He described a male adult with CM-I and syncope brought on by sneezing.
In 1978, BH Dobkin reported an adult patient with CM-I presenting with recurrent syncope with “modest neck extension”. EEG showed transient slowing but no seizures.
In 1982 F. Hampton, Bernard Williams and La Loizou, presented three cases with CM-I/syringomyelia and syncope. A 52 y/o woman without warning would blackout while standing. She had one further episode after posterior fossa decompression. Blackouts were preceded by headache in a 20 y/o man and in a 21 y/o man whose headache and blackout occurred when straining to urinate. Both had resolution of syncope following posterior fossa decompression.
In 1991, Weig et al. described two patients with frequent syncope and CM-I. A 23 y/o woman had syncopal episodes, most after head movement. She would develop vertigo, become dazed, and “within seconds, lose consciousness for 1-2 minutes.” She had been diagnosed with complex partial seizures or basilar migraine. EEG was normal. Spells resolved following posterior fossa decompression. A 22 y/o man developed arm weakness with coughing followed in 30 to 60 seconds by syncope. EEG was normal. His spells resolved after surgical decompression.
Also in 1991, Cirignotta et al. described a case of “convulsive non-epileptic attacks” in a 51-year-old man with CM-I. The following year, Alarcon et al. reported a 66 y/o woman with CM-I and syringomyelia had headache, syncope, blurred vision, and “an "electric-like" paroxysmal tingling of the hands” with coughing. In 1993, Palma et al. reported two young women with CM-I and syncope.
Loss of consciousness and apnea followed by cardiac arrest was described by Alegre et al. in a 31 y/o man after “brisk head movement.” Spontaneous recurrent apnea as the sole symptom of CM-I was reported by Martinez Soto et al. in 1995. In 2002, Aguiar et al. described a person with glossopharyngela neuralgia and “episodes of syncope when eating or swallowing.”
In 1999, Ziegler & Mallonee report a case of sudden death in a person with “repeated attacks of headache and syncope.” Diagnosis had been basilar migraine prior to discovery of CM-I and syringomyelia. This is the only case of sudden death in the list.
In 2005, Prilipko et al. reported the first case of a person with CM-I with syncope and postural orthostatic tachycardia syndrome (POTS).
Summary of Cases
The syncopal episodes, sometimes referred to as blackouts, were transient except in two with serious consequences: cardiac arrest or sudden death.
Syncope was brought on by coughing or sneezing in 3 patients and by neck extension or turning in another 3. In one patient, syncope occurred with straining at urination. Some patients had a warning headache, while others no warning at all prior to the sudden loss of consciousness. EEG performed in four patients was negative for seizure.
While the number of cases of Chiari syncope reported in the literature is small, in 2004, Diane Mueller and I published a report on the symptoms occurring in 265 patients with the Chiari I malformation with or without syringomyelia. We found 6.8% reported blackout spells as one of their symptoms.
In their 1976 report, Corbett et al. proposed “pressure transmission to the area of intracranial pathology” as the mechanism of syncope in CM-I. Subsequent authors supported brainstem compression as the likely cause.
Ventricular and lumbar CSF pressures were measured in two patients in the Hampton et al. study. Pressure dissociation was demonstrated in a patient with episodes of apnea and cough headache. This supports a pressure differential at the level of the foramen magnum as a factor in triggering syncope.
In 1996, a prospective study by Ireland et al. measured the autonomic cardiovascular responses in 7 patients with CM-I and 2 patients with CM-II. Three of these patients had cough syncope while the others had cough headache, chronic headache, or other neurological symptoms. “Preoperatively, all patients exhibited abnormal control of heart rate in response to postural change.”
Five patients underwent surgery and each had resolution of their symptoms. Cardiovascular responses returned to normal on post-operative testing. These findings support abnormal autonomic control of heart rate as the underlying factor in persons with Chiari syncope.
In summary, brainstem compression in persons with Chiari syncope is likely due to dysfunction of autonomic control of the heart. If this dysfunction is significant enough, sudden loss of consciousness may occur without warning. In some, syncope is brought on by postural change and autonomic regulation is not able to respond adequately. In others, increased tonsillar impaction as seen with coughing or sneezing, or compression/distortion as may occur with head extension or turning, is enough to trigger failure of cardiac autonomic control.