bouncebacks: posterior circulation stroke

posterior circulation

Posterior circulation strokes are less common and have a wide spectrum of symptoms and signs, so it’s not surprising they are easily missed. Here are a few misses/near misses, and their associated misdiaganoses

 

‘GASTRO’

60yoM with a history of DM/HTN presents with dizzy/vomiting all day, one diarrhea. No documented neuro exam, given fluids and gravol, felt better and sent home. Returns a few days later with constant dizziness, blurred vision, unstable gait. Normal CT head. MRI showed cerebellar infarct.

 

‘VERTIGO’

40yoM sudden headache, vertigo. Normal neuro exam except unable to walk, improved with fluids/gravol and sent home. Returned a few days later with ongoing vertigo, unilateral facial paresthesias. CT showed cerebellar infarct, and CTA showed vertebral artery dissection. On further history he had strained his neck at the gym.

 

‘MIGRAINE’

30yoM with history of migraines, worse for 1 week after working out, with on/off neck pain, hearing loss, vision changes. Seen at a couple of walk in clinics that prescribed muscle relaxants. CTA showed vertebral artery dissection.

 

‘STROKE’

70M AF/DM/HTN on pradax, with sudden dizzy, vomiting, diplopia. On exam cranial nerve palsy and motor weakness. CT head reported as normal but re-read by neurologist as basilar artery thrombus and sent for urgent embolectomy.

 

Lessons

  1. Posterior circulation stroke are rare mimics of common complaints, and can affect all age groups: consider in all patients with “gastro”, “vertigo”, and “migraine,”
  2. Ask about risks for thrombosis (DM, HTN, lipid), embolism (AF, valve) and dissection (neck strain/trauma), and document a full neuro exam including cranial nerves (along with HINTS exam), coordination and gait
  3. CT scans have a very poor sensitivity for posterior circulation stroke, consider CTA neck and MRI if you’re concerned or can’t explain the symptoms
  4. if you’re worried consult neurology early to re-read the CT and consider more advanced treatment, eg embolectomy for basilar stroke

 

HINTS test for vertigo

  • Head Impulse: central vertigo has normal head impulse (preserved vestibulocochlear reflex, as opposed to abnormal lag in peripheral)
  • Nystagmus: central vertigo has vertical or bidirectional nystagmus
  • Test of Skew: central vertigo has skew deviation in response to cover/uncover test

 

To help localize brainstem strokes read The rule of 4 of the brainstem: a simplified method for understanding brainstem anatomy and brainstem vascular syndromes for the non-neurologist. Int Med J 2005;35:263-266

  1. 4 midline structures with M:
    1. Motor (corticospinal) –> contralateral weak
    2. Medial lemniscus –> contralateral loss vibration/proprioception
    3. Medial longitudinal fasciculus –> ipsilateral INO
    4. Motor nucleus –> ipsilateral CN palsy
  2. 4 lateral structures with S
    1. Spinocerebellar –> ipsilateral ataxia
    2. Spinothalamic –> contralateral loss pain/temp
    3. Sensory nuclear of CN V –> ipsilateral alter pain/temp face
    4. Sympathetic –> ipsilateral Horner’s
  3. 4 cranial nerves in medulla (8-12), 4 in pons (5-8), and 4 above pons
  4. 4 motor nuclei in midline: 4, 6, 12

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