Posterior circulation stroke

posterior circulation stroke

a type of cerebral infarction affecting the  posterior circulation that supply one side of the brain.            Posterior circulation ischemia can range from brainstem symptoms, caused by reduced posterior circulation,

to the “locked-in syndrome,” which is caused by basilar artery or bilateral vertebral artery occlusion.

                                           The posterior cerebral arteries (PCAs) are paired vessels,
 usually arising from the top of the basilar artery and curves laterally, posteriorly, and superiorly
 around the midbrain. The PCA  mainly supplies midbrain, subthalamic nucleus, basal nucleus, thalamus,
medial inferior temporal lobe, and occipital and occipitoparietal cortices. PCAs, via the posterior
 communicating arteries (PCOM), may become sources of collateral circulation for the middle
cerebral artery (MCA)

PCA is divided into P1 and P2 segments by the PCOM. Penetrating branches to the mesencephalon, subthalamic, basal structures, and thalamus arise primarily from the P1 segment and the PCOM. These penetrating arteries include the thalamogeniculate, splenial (posterior paricallosal artery), and lateral and medial posterior choroidal arteries.

The P2 segment  is divided into the posterior temporal artery and the internal occipital artery. The posterior temporal artery further divides into anterior, middle, posterior, and hippocampal branches. The internal occipital artery divides into calcarine and occipitoparietal branches.

                                                   Posterior Circulation Stroke Syndrome (POCS) refers to the symptoms of a patient who suffered from a posterior circulation infarct, but clinically no diagnosis is there. PCA stroke syndromes comprises of

    • Paramedian thalamic infarction
    • Visual field loss
    • Visual agnosia
    • Balint syndrome
    • Prosopagnosia
    • Palinopsia, micropsia, and macropsia
    • Disorders of reading
    • Disorders of color vision
    • Memory impairment
    • Motor dysfunction
                        etiologyof posterior circulation stroke  
                         Ischemic stroke occurs when a region of cerebral blood flow is suddenly limited.. Common  causes of PCA stroke include
cardiogenic embolization,
atheromatous disease of proximal vessels resulting in occlusion and/or artery-to-artery embolization,
dissection of proximal vessels resulting in occlusion and/or artery-to-artery embolization,
intrinsic PCA atheromatous disease.
                                                                     Less common etiologies include
 migrainous cerebral infarction (which preferentially affects the PCA distribution),
anterior circulation disease (when fetal PCA variant is present),
hypercoagulable disorders,
illicit substance use,
vasculitis

   signs and symptoms of posterior circulation stroke

Patients present with a wide variety of syndromes. Neurological dysfunction includes
 1) hemi or quadriparesis,
 2) cranial nerve deficits (III-XII),
 3) respiratory difficulty,
 4) altered sensorium,
 5) vertigo  6) ataxia.
        As the posterior circulation supplies the brainstem, cerebellum, and occipital cortex,
 the symptoms frequently involve the "5Ds": dizziness, diplopia, dysarthria, dysphagia, and dystaxia.
                             Wallenberg Syndrome or Lateral Medullary Syndrome is characterized by
 sensory loss. Vertebral artery and posterior inferior cerebellar artery occlusion causes
 nystagmus,vertigo, ataxia, hoarseness, dysphagia, Horner's Syndrome and loss of pain and temperature
sensation in the face on the same side of the lesion, and loss of pain and temperature on the opposite side of the body.               Basilar Syndrome (Anton Syndrome) is caused by occlusion of the basilar artery tip as it bifurcates into the posterior cerebral arteries therefore also affecting the occipital lobes and
deeper structures which results in somnolence, memory defects, confusion, mutism, visual hallucinations, and bilateral loss of vision with unawareness or denial of blindness, as well as vertical gaze paralysis and deviation of the eyes.
              Weber Syndrome is caused by vascular occlusion to the midbrain  which may be due to aneurysm
or tumor resulting in ipsilateral oculomotor palsy  with contralateral hemiplegia.                                Dejerine-Roussy Syndrome occurs due to ischemia or malignancy causing a
hemi sensory loss  on one side of the body, contralateral to the side of the lesion. Position sense is
affected more than any other sensory function, and deep sensory loss is  more than cutaneous sensory loss.
    The most dreaded posterior circulation infarction is the "Locked-In Syndrome," which is caused by basilar artery occlusion. The syndrome is characterized by a progression of symptoms leading to
quadriplegia with paralysis of horizontal gaze and bilateral facial and oropharyngeal palsy.  The patient
is awake and is only able to move his or her eyes vertically.Patients become stuporous or comatose as the
reticular activating system becomes involved.
                       Treatment of posterior circulation stroke
  anticoagulants of the heparin and warfarin types were being used to treat patients with myocardial
infarction and pulmonary embolism. management of hypertension, hyperglycemia, cerebral edema with
increased intracranial pressure, hemorrhagic transformation of cerebral infarction, infections aspiration,
 deep venous thrombosis, myocardial infarction, and other stroke-associated conditions.
 recombinant tissue-type plasminogen activator( rtPA) should be  administered within 3 hours of stroke onset
 Extracranial bypass may be undertaken by connection of the occipital artery to the vertebral, superior cere
bellar, anterior ICA, or posterior ICA. The superficial temporal artery has also been used as a donor artery.
Shunting to the PCA may be accomplished by using veins or synthetic grafts.
                                      rehabilitation should begin early. Involvement of a speech  therapist may be required if alexia is present, with or without aphasia. The occupational therapist should be able to help in  teaching patients to turn to look in the blank visual hemifield. Recreational therapy helps patients with posterior cerebral artery (PCA) stroke to adapt to visual deficits and facilitates a healthy affect (since depression is a common occurrence in stroke.Nutrition may need to be provided by alternative means, such as a nasogastric device or a percutaneous enteric gastrostomy tube in patients who have severe dysphagia. revascularization procedures in the posterior circulation is the prevention of vertebrobasilar ischemic stroke.


Article publié pour la première fois le 18/10/2011

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