AVM is a conglomerate of abnormal vessels( both arterial and venous) of variable size and number with no intermediate capillary network and there is no parenchyma among vessels.Both the feeding arteries and the draining veins are tortuous and dilated.
According to Mc Cormick's description ( Classification of vascular malformations of brain, 1978), the common vascular malformations of the brain are:
-AVM
-Cavernous angiomas
-Venous angiomas
-Capillary telangiectasia, &
-Transitional forms
The majority of the patients present in the third decade and another peak in the pediatric age group. Only 18-20% of cerebral AVMs are diagnosed during infancy and childhood. The onset of symptoms is maximal in the second & third decades, although these lesions are present since birth. This latency in in the onset of symptoms is probably due to progressive maturation and growth of the lesion and gradual changes in the adjacent brain parenchyma ( Like hemorrhage and gliosis causing headache, seizures, focal neurological deficit).
Intracranial hemorrhage is the most common mode of presentation of AVMs, with the majority of having bled before the age of 40 years. Seizures is the second most common manifestation followed by neurological deficits and mental changes as the result of arterial steal, venous hypertension causing hypoperfusion of the surrounding brain parenchyma and mass effect.
In a very large AVM with enlargement of the feeding vessels & increased blood flow there may be associated change in the pulse pressure giving rise to a water hammer pulse. In late stages high output cardiac failure may result.
Hemispheric AVMs are located in the middle cerebral , posterior cerebral and anterior cerebral territories in declining frequencies. Hemispheric AVMs situated in the watershed areas are usually supplied by more than one arterial pedicle. The parietal lobe is the commonest region involved in supratentorial lesions. The majority of deep AVMs are located in the medial paratrigonal region.
In 1986, Spetzler and Martin published most practical classification taking into account size, location and venous drainage.
Points are assigned for each factor as follows:
1. Size of AVM
Small ( less than 3 cm) 1 point
Medium ( 3-6 cm) 2 point
Large ( more tha 6 cm) 3 point
2. Location of AVM ( Eloquence of adjacent brain)
Non-eloquent 0 point
Eloquent 1 point
3. Pattern of venous drainage
Superficial only 0 point
Deep 1 point
The grades are 1 to V and is arrived at by adding the scores.
Grade 1, i.e., a small AVM in a non-eloquent area with a superficial drainage has the best prognosis; and grade V ,i.e., a large AVM in an eloquent area with deep venous drainage has the worst prognosis.
The term "Eloquent" is used for areas of cortex that, if removed will result in loss of sensory processing or linguistic ability, minor paralysis, or paralysis.
The risk of post-surgical neurological deficit (difficulty with language, motor weakness, vision loss) increases with increasing Spetzler-Martin grade.
There are five options for treating AVMs:
1.Expectant behavior
2.Excisional Surgery: Total surgical excision is the gold standard treatment.
3.Endovascular therapy: Interventional radiologists can embolise the AVM nidusor the feeders as definitive treatment.
4.Radiosurgery is indicated for AVM of less than 3 cm size.
5.Combination of the above options
According to Mc Cormick's description ( Classification of vascular malformations of brain, 1978), the common vascular malformations of the brain are:
-AVM
-Cavernous angiomas
-Venous angiomas
-Capillary telangiectasia, &
-Transitional forms
The majority of the patients present in the third decade and another peak in the pediatric age group. Only 18-20% of cerebral AVMs are diagnosed during infancy and childhood. The onset of symptoms is maximal in the second & third decades, although these lesions are present since birth. This latency in in the onset of symptoms is probably due to progressive maturation and growth of the lesion and gradual changes in the adjacent brain parenchyma ( Like hemorrhage and gliosis causing headache, seizures, focal neurological deficit).
Intracranial hemorrhage is the most common mode of presentation of AVMs, with the majority of having bled before the age of 40 years. Seizures is the second most common manifestation followed by neurological deficits and mental changes as the result of arterial steal, venous hypertension causing hypoperfusion of the surrounding brain parenchyma and mass effect.
In a very large AVM with enlargement of the feeding vessels & increased blood flow there may be associated change in the pulse pressure giving rise to a water hammer pulse. In late stages high output cardiac failure may result.
Hemispheric AVMs are located in the middle cerebral , posterior cerebral and anterior cerebral territories in declining frequencies. Hemispheric AVMs situated in the watershed areas are usually supplied by more than one arterial pedicle. The parietal lobe is the commonest region involved in supratentorial lesions. The majority of deep AVMs are located in the medial paratrigonal region.
In 1986, Spetzler and Martin published most practical classification taking into account size, location and venous drainage.
Points are assigned for each factor as follows:
1. Size of AVM
Small ( less than 3 cm) 1 point
Medium ( 3-6 cm) 2 point
Large ( more tha 6 cm) 3 point
2. Location of AVM ( Eloquence of adjacent brain)
Non-eloquent 0 point
Eloquent 1 point
3. Pattern of venous drainage
Superficial only 0 point
Deep 1 point
The grades are 1 to V and is arrived at by adding the scores.
Grade 1, i.e., a small AVM in a non-eloquent area with a superficial drainage has the best prognosis; and grade V ,i.e., a large AVM in an eloquent area with deep venous drainage has the worst prognosis.
The term "Eloquent" is used for areas of cortex that, if removed will result in loss of sensory processing or linguistic ability, minor paralysis, or paralysis.
The risk of post-surgical neurological deficit (difficulty with language, motor weakness, vision loss) increases with increasing Spetzler-Martin grade.
There are five options for treating AVMs:
1.Expectant behavior
2.Excisional Surgery: Total surgical excision is the gold standard treatment.
3.Endovascular therapy: Interventional radiologists can embolise the AVM nidusor the feeders as definitive treatment.
4.Radiosurgery is indicated for AVM of less than 3 cm size.
5.Combination of the above options
No comments:
Post a Comment