Pearls on Intracranial atherosclerosis

Turan TN, Chimowitz MI.  . 10 questions about intracranial atherosclerosis.The Neurologist. 16:6 400-405 1020.

1.  MRA and TCD have high negative predictive values but low positive predictive values for detecting intracranial stenosis.  (86-91. v. 36-59 % respectively).  They are therefore adequate screening tests but need CTA for diagnosis or catheter angiography.  CTA studies have limited statistical power therefore catheter studies are the "gold standard" to determine the degree of stenosis, but also confer risk.  A single preliminary study showed CTA had a sensitivity and specificity to detect intracranial stenosis greater than 50 % of of 97.1 and 99.5 % respectively.  In ACAS the risk of stroke with catheter angiography was 1.2 %. The SONIA study was the study that helped evaluate the above.

2.  The risk of stroke with intracranial stenosis is the highest of any stroke subtype, with respect to symptomatic stenosis  of greater than 50 %.  The risk of ischemic stroke in any territory within two years was 20 % in aspirin arm and 17 % in the warfarin arm (WASID).  Over 70 % of strokes occurred in the same territory.  Thus the risk in the symptomatic artery was 15/13 % in aspirin and warfarin arms respectively.  This is higher than the risk with atrial fibrillation or cardioembolic stroke.

3.   The risk of stroke was proportional to the severity of stenosis (risk of stroke within the symptomatic artery occurred in 6/18 % of patients, respectively, with < 70 and >70 % stenosis. 

4.  Other risk factors for stroke in the territory included recent symptoms, female gender, and baseline NIHSS >1.  Vertebrobasilar arterial disease was NOT a risk factor. 

5.  Asymptomatic stenosis was very low risk, with a one year risk of stroke of 0 % in one study and 3.5 % in WASID by MRA. 

6.  "Antithrombotic failures" ie patients already on antiplatelet drugs at time of their stroke, were not at higher risk for recurrent stroke than patients who were not on antiplatelet drugs at the time of their qualifying event. 

7.  Most important risk factors for recurrent stroke were dyslipidemia and hypertension  (SBP> 140). 

8.  SSYLVIA (stenting of symptomatic atherosclerotic lesions in the vertebral or intracranial arteries) was a ph I study of a bare metal stent that showed technical success and a 10.9 % stroke rate in one year with all strokes within the same artery. 

9.  SSAMPRIS study is ongoing (Stenting and Aggressive Medical Management of for Prevention of Recurrent Stroke in Intracranial Stenosis) NIH sponsored study.  In 764  patients it compares angioplasty and stenting plus aggressive medical management v. medical management alone in patients with 70-99 % stenosis.  Patients must have a TIA or nondisabling  stroke within 30 days in an appropriate artery to be eligible.  The protocol includes ASPIRIN for duration, plavix for first 90 days, aggressive bp and lipid management.

10.  See http://www.ssampris.org/ or http://www.sammpris.org/.

HINTS to diagnose stroke in acute vestibular syndrome: 3 step oculomotor exam

 

Stroke. 2009 Nov;40(11):3504-10. Epub  2009 Sep 17.
HINTS to diagnose stroke in the acute vestibular syndrome: three-step bedside oculomotor examination more sensitive than early MRI diffusion-weighted imaging.
Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE.
Department of Neurology, The University of Illinois College of Medicine at Peoria and the Illinois Neurological Institute at OSF Saint Francis Medical Center, Peoria, Ill, USA.

Abstract
BACKGROUND AND PURPOSE: Acute vestibular syndrome (AVS) is often due to vestibular neuritis but can result from vertebrobasilar strokes. Misdiagnosis of posterior fossa infarcts in emergency care settings is frequent. Bedside oculomotor findings may reliably identify stroke in AVS, but prospective studies have been lacking.
METHODS: The authors conducted a prospective, cross-sectional study at an academic hospital. Consecutive patients with AVS (vertigo, nystagmus, nausea/vomiting, head-motion intolerance, unsteady gait) with >or=1 stroke risk factor underwent structured examination, including horizontal head impulse test of vestibulo-ocular reflex function, observation of nystagmus in different gaze positions, and prism cross-cover test of ocular alignment. All underwent neuroimaging and admission (generally <72 hours after symptom onset). Strokes were diagnosed by MRI or CT. Peripheral lesions were diagnosed by normal MRI and clinical follow-up.
RESULTS: One hundred one high-risk patients with AVS included 25 peripheral and 76 central lesions (69 ischemic strokes, 4 hemorrhages, 3 other). The presence of normal horizontal head impulse test, direction-changing nystagmus in eccentric gaze, or skew deviation (vertical ocular misalignment) was 100% sensitive and 96% specific for stroke. Skew was present in 17% and associated with brainstem lesions (4% peripheral, 4% pure cerebellar, 30% brainstem involvement; chi(2), P=0.003). Skew correctly predicted lateral pontine stroke in 2 of 3 cases in which an abnormal horizontal head impulse test erroneously suggested peripheral localization. Initial MRI diffusion-weighted imaging was falsely negative in 12% (all <48 hours after symptom onset).
CONCLUSIONS: Skew predicts brainstem involvement in AVS and can identify stroke when an abnormal horizontal head impulse test falsely suggests a peripheral lesion. A 3-step bedside oculomotor examination (HINTS: Head-Impulse-Nystagmus-Test-of-Skew) appears more sensitive for stroke than early MRI in AVS.

neurodoc

Patient foramen ovale

Kent DM, Thaler DE.  Is Patent foramen ovale a modifiable risk factor for stroke recurrence?Stroke 2010: 41 (supplement 1) S 26-S30.

Authors make statistical arguments about PFO management.  Facts that form a basis:

1.  PFO occurs in 25 % of autopsies.
2.  PFO occurs in a higher rate in cryptogenic stroke, but in at least 33 % of strokes with PFO the PFO is incidental.
3.  PFO in Cryptogenic Stroke Study (PICSS) shows near identical stroke recurrence risk in patients with cryptogenic stroke whether or not they have a PFO.  Further, small PFO's had a higher recurrence rate than large ones.  This simply indicates, however, that PICSS included patients who were eventually given a TEE , even if they had a different defined mechanism for their stroke.  Other occult mechanisms such as occult afib or subthreshold aortic atherothrombotic disease may have a higher recurrence rate.
4.  Consistently, studies show that patients with cryptogenic stroke and PFO have less conventional stroke risk factors than patients without PFO.  Since recurrence risk of stroke is about equal in PFO + and - patients, PFO singlehandedly compensates for lack of other risk factors.  Therefore, PFO IS a risk factor for stroke.  Younger patients without DM or HTN are much more likely to have a PFO. 
5.  When a PFO is found in setting with an atrial septal aneurysm, the PFO is rarely incidental to the stroke.
6.  "PFO propensity" is likelihood based on age or other factors that a CS patient has a PFO.  A higher PFO propensity correlates with a lower chance of incidental PFO.  A younger patient without other risk factors may have a very high PFO propensity and therefore probability of nonincidental PFO. 
7.  The margin of benefit in PFO closure is narrow.  Even a low rate of procedure complications could nullify benefit.  "Testing the procedure (closure) in a population in which many incidental PFOs occur may falsely suggest the procedure is of no benefit."