Posterior circulation strokes involve the vertebrobasilar arteries and account for about one-fifth of ischemic strokes. They are associated with a high risk of early recurrent stroke. Clinical features can include dizziness, limb weakness, dysarthria, and nausea. Investigations like MRI and MRA are important for diagnosis but may be normal for small brainstem infarcts. There is a higher risk of early recurrent stroke after posterior circulation events compared to carotid events. Secondary prevention focuses on antiplatelet drugs and controlling risk factors like blood pressure, though aggressive lowering is not recommended in some cases of vertebrobasilar stenosis due to risk of recurrent stroke.

1. Posterior circulation ischaemic
stroke and TIA:
Diagnosis, investigation, and
secondary prevention

2. Introduction
• One Fifth of all TIA’s and ischemic attacks are
in the territory of the vertebrobasilar
circulation.
• They are associated with high risk of early
recurrent stroke.
• Secondary prevention is important.
• There are particular challenges in
diagnosis, investigations and treatment.

3. Anatomy
• Vertebral Artery – Has an intracranial and
extra cranial part. Lumen diameter(3-5mm)
• Unilateral hypoplasia (<= 2mm) is present in
25% of normal individuals(MRA). But it is
more commonly seen in patients with
posterior circulation stroke.
• This suggests that the narrowing was caused
by atherosclerosis, in these patients.

4. • PICA(Posterior inferior cerebellar artery) is a
branch of INTRACRANIAL vertebral artery.
• In up to 20% cases it may arise
EXTRACRANIALLY.
• Rarely it may arise from basilar artery.

5. Basilar artery-Branches
•
•
•
•
AICA(Anterior inferior cerebellar artery)
Pontine arteries.
Superior cerebellar arteries
Posterior cerebral artery.
• For each of these arteries, anatomical variants
have been described.

7. PCA(Posterior cerebral artery)
• Arise as terminal bifurcation of basilar artery.
• In 50% of population, Internal carotids
significantly contribute to the posterior
circulation via the PCOMs.
• In 10% of population, The P1 segment is
absent and PCA is exclusively supplied by the
internal carotids.

8. Disease mechanisms.
• Cardioembolism.
• Large artery atherosclerosis.
• Small Artery disease.

9. • Atherosclerosis OFTEN occurs at or near the
ORIGIN of the vertebral artery.
• Also occurs in distal vertebral artery and
basilar arteries.

10. • Atherosclerotic narrowing by itself rarely
causes ischemia- In a registry only 13 0f 407
patients had hemodynamically significant
atherosclerotic obstruction.
• THROMBOEMBOLISM from the site of arterial
stenosis seems to be the predominant cause
of ischemia.

11. Small vessel disease- Lacunar infarcts
• Lipohyalinotic thickening of vessels in the
background of hypertension.
• Focal atherosclerosis of the penetrating
vessel.
• Patients with lacunar infarcts have been found
to have co-existng large artery
atheroscleroseis, and/or cardioembolic
source.

12. • Vertebral artery dissection is an important
cause of posterior circulation stroke in the
young.

13. Clinical features.
(Sample size of 407 patients)
Symptoms
• Dizzyness
(47%)
• Unilateral Limb weakness(41%)
• Dysarthria
(31%)
• Headache
(28%)
• Nausea & vomitnig
(27%)

14. Signs
• Unilateral limb weakness (38%)
• Gait ataxia
(31%)
• Unilateral Limb ataxia
(30%)
• Dysarthria
(28%)
• Nystagmus
(24%)

15. • The findings may also occur in isolation.
Notably,..
• Isolated vertigo.
• Isolated Cranial nerve palsies.
• Internuclear ophthalmoplegia.
• Ptosis
• Dysphagia, dysarthria
• Deafness

16. • Labyrinthine artery (branch of AICA) supplies
the inner ear.
• Occlusion may lead to symptoms of vertigo
and hearing loss.

17. • In patients with isolated symptoms, there are
no clinical signs that can reliably differentiate
between cerebellar and brainstem ischemia
and a non-vascular cause of the isolated
symptoms.

18. Posterior circulation TIA and risk for
stroke.
• Isolated TRANSIENT brainstem symptoms
were 12 times more frequent in the 90 days
before vertebrobasilar stroke. (when compared to carotid
stroke)
• 30 times more frequent during the preceding
2 days.

19. Accuracy of clinical diagnosis
• Sensitivity (54-.2% - 70.8%)
• Specificity (84.4% - 89.9%)
• In a study in which three independent
neurologists diagnosed the most likely
vascular territory.

20. Investigations
• MRI is more sensitive than CT. Especially in the
brainstem.
• Particularly if diffusion weighted imaging is
done during the acute phase.
• However they can be negative for clinically
definite posterior circulation
infarcts, particularly small brainstem infarcts.

21. • Duplex- Ultrasound is less sensitive in
detecting vertebral artery stenosis
• CT Angiography and Contrast Enhanced MR
Angiography allow visualisation of the entire
vertebrobasilar arterial tree.
• CE-MRA has the highest sensitivity and
specificity.

22. Risk of recurrent stroke after an
ischemic event.
• In the ACUTE phase, there is a higher risk of
EARLY recurrent stroke after vertebrobasilar
events, when compared to carotid ischemic
events.
• These patients have high prevalence of
vertebrobasilar stenosis, which itself is
associated with high prevalence of recurrent
stroke

23. • Risk of recurrence during the first
year, however was similar in both
vertebrobasilar and carotid TIA.
• In patients with vertebrobasilar TIA, the
absolute risk of stroke at 1 year was 17.1%

24. Secondary Prevention.
• Similar to that of stroke in general.
• Clopidogrel Alone or Aspirin-Dipyridamole
combination is recommended.
• Evidence from trials suggest that AspirinClopidogrel combination is more effective, with
an acceptable risk factor profile for EARLY
prevention of recurrent stroke.
• i.e for the first few months after the ischemic
event to cover the period of increased risk.

25. • Blood pressure lowering is beneficial in most
patients.
• Aggressive blood pressure reduction is to be
avoided in patients with bilateral vertebral
artery stenosis, severe unilateral stenosis, or
severe basilar artery stenosis, as it increases
the risk of recurrent stroke.(SBP<140mmHg)

26. Endovascular treatment
• Angioplasty and/or stenting.
• No evidence from RTC’s to identify whether it
is superior to best medical treatment.
• The only Completed RTC had 16
patients, which is too small a number to draw
strong conclusions.

27. Surgical management.
• Surgery is rarely undertaken to treat vertebral
artery stenosis, when compared to carotid
endarterectomy.
• Surgical access is less easy in vertebral artery
stenosis.

28. Future directions.
• Better diagnostic aids are needed for the benefit
of a substantial minority of cases.
• New factors are needed to differentiate reliably
between CVA and Non-vascular causes of isolated
and transient neurological symptoms.
• Randomised controlled trials are needed to
identify whether intervention with stenting can
reduce the risk of stroke in cases of symptomatic
vertebral artery stenosis.