Stroke Syndromes or "What You Talkin' 'Bout (Circle of) Willis?"

David Bertoni

The academic/functional territories of the brain are an important foundation - this knowledge consumed in medical school doesn’t translate precisely into discrete territory deficits that we see come through the turnstiles. This is because these functional areas do not have discrete vessel-for-territory vascular supply. Nevertheless, they do form distinct patterns of deficit when compromised - or "Stroke Syndromes". Here is a simple systematic way of differentiating supply issues for these neurons.

Objectives

• Review basic & relevant neuroanatomy
• Describe an approach to stroke localisation based on clinical findings (ant vs post)

FRONTAL // Personality changes, anosmia, gait apraxia, leg weakness,urinary incontinence, expressive dysphasia
PARIETAL // Dysphasia, Gerstmann's syndrome (dominant) / Sensory inattention, dressing / constructional apraxia (non-localising)
TEMPORAL // Memory loss, receptive dysphasia (dominant)
OCCIPITAL // Homonymous hemianopia (contralateral)

Some Stats (unreferenced)

• Approx 80% ischaemic, 20% haemorrhagic
• Approx 80% anterior circulation, 20% vertebrobasilar
  
• In young and middle aged, approx 20% of non-haemorrhagic strokes are caused by cervical artery dissection
  

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Functional Anatomy

Tip: Broca's area is closest to motor cortex, therefore is the motor part of speech

Gerstmann's Syndrome
Dysgraphia + Dyscalculia + Finger Agnosia + L-R Disorientation

Vascular Supply to the Brain

In general, the most difficult & important aspect of understanding the vascular supply to the brain is to appreciate that it has an 

1. ANTERIOR (from the internal carotid arteries) and 
2. POSTERIOR (from the vertebrobasilar arteries) circulation. 

Features of Posterior Circulation Strokes

1     Ipsilateral CN signs with contralateral limb motor or sensory signs?
2     Multiple CN involved?
3     Vertigo, ataxia, nausea, 'dizziness', dysarthria, cerebellar signs?
4     Absence of Cortical signs? (e.g aphasia, cognitive defects)

Vascular 'Territories'

As you can see from the diagrams (right), laterally much of the supply is from the MCA (red) and medially is the ACA (yellow). 

If you match the vascular territory with the homunculus you can appreciate what deficits you might find based on the deficient vessel.

ACA    
UMN leg > arm, sensory loss leg, urinary incontinence (variable)

MCA    
UMN + sensory loss face, arm > leg, homonymous hemianopia, dysphasia (dominant), neglect (non-dominant)

PCA    
Heminanaesthesia (thalamus), homonymous hemianopia, alexia, visual hallucination

Lacunar   
Pure motor / sensory / sensorimotor hemiparesis (no cortical signs), ataxic hemiparesis, dysarthria – clumsy hand syndrome.

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Brainstem Strokes (aka Posterior Circulation Strokes)

Peter Gate's developed a "Rule of 4s for the brainstem" to simplify stroke syndromes:

1. 4 CNs are divided into 3 groups; Midbrain, Pons, Medulla
   
2. 4 M's (Motor nuclei, MLF, motor tracts, medial lemniscus)
   
3. 4 S's (Spinocerebellar, spinothalamic, sensory nucleus of 5th CN, sympathetic)
   
4. 4 Medial CNs nuclei divisible into 12 (3,4,6,12), others are lateral

 NB Above rules used as meridians of longitude / latitude

Video here
Article here 

LATERAL

SC (Spinocerebellar)

• Ipsilateral ataxia of the limbs

SP (Spinothalamic)

• Contralateral loss of temperature & pain in the limbs

SY (Sympathetic)

• Ipsilateral Horner's*

SV (Sensory Nucleus of 5th CN)

• Ipsilateral loss of temperature & pain in the face

*Partial Ptosis, Meosis & Anhidrosis

MEDIAL

MN (Motor Nucleus 3, 4, 6 or 12)

• Ipsilateral loss of extraocular muscles and/or motor to tongue

MLF (Median Longitudinal Fasciculus)

• Ipsilateral inter-nuclear opthalmoplegia**

ML (Medial Lemniscus)

• Contralateral loss of vibration & proprioception in the limbs

MP (Motor Pathway aka Corticospinal Tract)

• Contralateral weakness of limbs

**absent ipsilateral eye adduction and contralateral abducted nystagmus

Test Cases To Determine Territory Deficit

CASE 1

Weakness of left upper / lower limbs with facial sparing, loss of vibration & proprioception left upper / lower limbs. Tongue deviation to right.

1. Left limb weakness suggests contralateral corticospinal tract deficit ie R medial deficit
2. Left limb loss of V&P suggests contralateral medial lemniscus deficit ie R medial deficit
3. Tongue deviation to R suggests ipsilateral CN XII deficit ie R medial deficit
4. CN XII deficit suggests deficit is in medulla

Conclusion: Right Medial Medullary Ischaemia

CASE 2

Right limb ataxia, right sided facial numbness, right facial weakness

1. Right limb ataxia suggests ipsilateral spinocerebellar deficit ie Right lateral deficit
2. Right CN V deficit suggests ipsilateral sensory nucleus V deficit ie Right lateral deficit
3. Right CN VII deficit suggests deficit is in Pons

Conclusion: Right Lateral Pontine Ischaemia

CASE 3

Left limb ataxia, abnormal left pain / temperature perception in face, left Horner's syndrome, left absent gag and palate elevation.   

1. Left limb ataxia suggests ipsilateral spinocerebellar deficit ie Left lateral deficit
2. Left face loss of P&T suggests ipsilateral sensory nucleus V deficit ie Left lateral deficit
3. Left Horner's suggests ipsilateral sympathetic deficit ie Left lateral deficit
4. Left absent gag elevation suggests deficit in CN IX and/or X ie deficit in Medulla & lateral
5. Absent palate elevation suggests deficit in CN X ie deficit in Medulla & lateral

Conclusion: Left Lateral Medullary Syndrome

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References

1. Caplan LR (2015). Posterior circulation cerebrovascular syndromes. www.uptodate.com
   
2. Filho JO (2015). Initial assessment and management of acute stroke. www.uptodate.com
   
3. Filho, JO (2015). Lacunar infarcts. www.uptodate.com
   
4. Gates, P. The rule of 4 of the brainstem: a simplified method for understanding brainstem   anatomy and brainstem vascular syndromes for the non-neurologist. Internal Medicine   Journal 2005; 35: 263-266.
   
5. Nickson, C. (2009) http://lifeinthefastlane.com/brainstem-rules-of-4/
   
6. Nickson, C. (2009) http://lifeinthefastlane.com/using-the-brainstem-1/
   
7. Tintinalli, JE editor in chief. Tintinalli's emergency medicine. A comprehensive study guide. 7th ed. [e-book]. McGraw-Hill; 2011 [cited 2015, Sep 12].
   
8. Talley NJ, O'Connor S. Clinical examination. A systematic guide to physical diagnosis. 6th ed. Sydney; Elsevier: 2010.