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Perinatal Stroke: Classification

Preamble

The following information is designed to provide a general education about perinatal stroke.
The information is based on current evidence from the medical literature and the collective experience of the Alberta Perinatal Stroke Project (APSP).
Information is kept current as best possible.
However, our field continues to have more questions than answers.
Therefore, differences in terminology and information may differ from other resources. Readers are encouraged to discuss inconsistencies and questions with our team in the clinic.

What is Perinatal Stroke?

Stroke typically refers to the blockage (ischemic stroke) or breakage (hemorrhagic stroke) of a blood vessel (artery or vein) in the brain. 
 

Perinatal refers to the timeframe that extends all the way from the middle of pregnancy (fetal life) through birth and the first month of life.

Perinatal strokes are focal diseases of brain blood vessels that lead to injury in the brain during the fetal or newborn period. Perinatal stroke is not just one disease as several specific types are now recognized.

 

What are the Different Types of Perinatal Stroke?

The following provides links to additional sites on some forms of perinatal stroke.
For others where such resources are lacking, we provide additional educational information.

Perinatal strokes can be accurately classified by considering the following factors:
1.    Type: Ischemic or hemorrhagic
2.    Blood vessel affected: Artery or vein
3.    Timing of injury: Before birth (fetal) or around time of birth
4.    Timing of symptoms: At birth or later in infancy

Considering these factors, and summarized in the figure below, the three most common forms of perinatal stroke are:

A. Neonatal AIS (NAIS)

This is an acute blockage (ischemia) of a brain artery recognized around birth.
Seizures are usually noticed in the newborn.
This leads to an MRI scan that confirms the recent stroke.
Imaging usually suggests the stroke has occurred sometime within the preceding days.

NAIS is the most studied variety of perinatal stroke.
Additional information about NAIS can be found here: Link

Other types of perinatal stroke occur at or before birth but are only recognized later in a child’s life.
Much less is known about these Presumed Perinatal Ischemic Strokes (PPIS).
Additional information is provided here.

B. Presumed Perinatal Ischemic Stroke (PPIS)

Many perinatal strokes are not recognized at birth.
This is usually because the baby shows no physical signs of their stroke, even when a large or multiple strokes have occurred.

Instead, parents begin to notice the consequences of the stroke later in the first year of life.
This is when the child begins to use the areas of the brain that have been injured by the stroke.

The most typical sign is an asymmetry in body movements where parents notice that one side of the body is moving better than the other. Children should not show a clear preference to be left or right handed before their first birthday, often much later than this.
Such weakness on one side in a young infant has often been called congenital hemiplegia or hemiplegic CP. The majority of these are due to a perinatal stroke.

Other neurological concerns may also arise in the first year such as seizures or other developmental difficulties.

In all these cases, a picture of the brain (preferably MRI) should be done.
In many cases, the MRI will show damage consistent with an old stroke.

Since this diagnosis is made retrospectively (after the fact), we use the term:
Presumed Perinatal Ischemic Stroke (PPIS).

Recent research has defined 2 main types of PPIS:

B1. Arterial Presumed Perinatal Stroke (APPIS)

This presumed perinatal ischemic stroke is very similar to neonatal AIS.
Both are due to an occlusion of a brain artery, usually by a blood clot.
The only difference may be the timing that symptoms are realized – at birth or later in infancy.
Examples of both NAIS and APPIS are shown in the figure below.

In APPIS, a child’s symptoms are recognized later in infancy.
This is usually when parents or physician notice one side does not move as well (hemiparesis).
APPIS can also present with seizures or other developmental concerns.

This leads to an MRI that scan that shows an old stroke consistent with an arterial occlusion.
Most APPIS are blockages of the middle cerebral artery or its branches.
As a result, the damage that occurs usually affects both the outer surface of the brain (cortex) as well as deeper (subcortical) areas of the brain.
The timing cannot be determined exactly but many APPIS may be the same as NAIS, the only difference being the time of when symptoms were seen.

B2. Periventricular Venous Infarction (PVI)

This presumed perinatal ischemic stroke is different than APPIS or NAIS in several ways.
PVI are fetal strokes because they occur well before birth while the baby is still in the womb.
The details of what happens with PVI are explained here in more detail and diagrammed in the Figure and animated video below.

The structure of the premature brain (less than 34 weeks gestation) is different.
A collection of blood vessels called the germinal matrix lies deep in the brain where they nourish growing brain cells.
The germinal matrix is located just below the ventricles – normal, fluid filled spaces in the brain.
Bleeding of the germinal matrix is the primary problem in PVI.
Why such bleeding occurs is not well understood.
The blood can spill into the neighboring ventricle (so-called intraventricular hemorrhage).

Germinal matrix bleeding can also lead to a blockage of veins that drain blood from a specific brain area. This blockage of blood flow in the vein may also lead to a blood clot forming and further blocking blood flow.

These medullary or terminal veins drain blood from the area just beside the ventricle or periventricular region. In PVI, the germinal matrix hemorrhage leads to such an impairment of blood drainage from the periventircular white matter that it becomes injured or infarcted (i.e. a stroke).

Hence the term periventricular venous infarction or PVI.

The periventricular area contains white matter – the insulated “wires” that carry information in the brain. PVI often occurs in an area where the white matter carrying information from the brain to move the opposite side of the body are present. These are called the corticospinal tracts. The result of many PVI is damage to the corticospinal tracts with subsequent weakness on the opposite side of the body (congenital hemiplegia or hemiplegic cerebral palsy).

A video animation of what occurs in PVI can be viewed here:

PVI is similar to APPIS in that the weakness is usually not appreciated at birth but only later in infancy.

PVI is different from APPIS in the timing of the stroke (before birth) and the areas of the brain affected. PVI damage is only in the periventricular, subcortical region and does not involve the cortex like APPIS. This may be one reason why the outcomes in PVI and APPIS are different (see below.

The other two forms of perinatal stroke are reviewed elsewhere:

Neonatal hemorrhagic stroke

ADDITIONAL FREQUENTLY ASKED QUESTIONS ON PERINATAL STROKE

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