Symptoms
The major symptoms and signs of an AVM are severe focal headaches that resemble migraines (often only in one side of the head), cranial bruit (intracranial murmurs), neurological deficits which include hemiparesis (weakness on one side of the body), dysarthria (diffuculty producing speech), sensory disturbances, aphasias (difficulty communicating or understanding speech), and dementia, intracerebral, subarachnoid, or subdural hemorrhage, and seizures. Rarely infants will exhibit hydrocephalus and heart failure as a result of a subtype of AVM, a Vein of Galen AVM. Exophthalmos (pulsation of the eye in the orbits) is also seen in certain types of AVMs, although very rarely.
The main risk posed to the patient by AVMs mainly stems from the likelihood of intracranial hemorrhage.
Hemorrhaging is the most serious symptom of AVMs. Various sources estimate that between 50-70% of patients with an AVM first present with intracerebral hemorrhage, usually between ages 20 and 301, 2, 3. The high incidence of hemorrhage in these patients is most likely attributable to the fact that, in an AVM, venous channels carry blood at arterial pressures, and the venous channels are usually abnormally inelastic1.
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The intraventricular
and intracerebral hemorrhage seen here was due to a ruptured vascular
malformation. The hemorrhage from such a lesion (which is most often
histologically an arteriovenous malformation--AVM) can be intracerebral or
extend into ventricles or subarachnoid space. Borrowed
from: by Edward C. Klatt MD, Department of Pathology,
University of Utah, Salt Lake City, Utah, USA |
The second most common presenting symptom of AVMs is seizures. Between 25-50% of patients have convulsions as an initial symptom1, 3. The seizures are initially focal or Jacksonian (beginning in one area of the brain and spreading to the whole brain), but usually develop into generalized seizures. Episodic illusory or visual hallucinatory experiences in a young person should be taken as warning signs of a possible AVM.
Other frequent symptoms include migraine-like headaches (15% of patients), intellectual deterioration (eventually developed by about half of patients), and bruit (10-25% of patients)3. Bruit can sometimes be used to roughly estimate the location the AVM. Back to top
The risks associated with AVMs are determined by many factors. The location of the AVM is important in assessing the risk posed to the individual by the malformation. AVMs found in the cerebellum or in the brain stem tend to cause more symptoms and hemorrhage at a younger age than AVMs located in the cerebral cortex. In addition they may obstruct the proper flow of cerebrospinal fluid and cause hydrocephalus.
Age
is an important determinant for the cumulative risk of hemorrhage (the
probability that a patient will have a hemorrhage sometime during his or her
lifetime). Studies of patients with
AVMs have shown that there is a 2-4% annual risk of hemorrhage1,4. It is important to note that the cumulative
risk is higher for younger patients.
Note that while the cumulative risk of hemorrhage varies inversely with
age, there is seemingly no correlation between the size, side, and site of the
AVM, age or sex of the patient, and the annual risk of an AVM to bleed. Factors that do increase risk are previous
hemorrhaging, prior partial or unsuccessful treatments, and drug use. Although 90% of patients survive the first
bleed associated with an AVM (Arteriovenous Malformations. Clinical Presentation, 1997), AVMs that have
bled once have a 25% chance to bleed again within four years (Sawitzke and
Teter, 1976). The following tables give
the cumulative risk for hemorrhage of a patient of a certain age, sex, and
race. Note that while race and sex do
not affect the annual chance of hemorrhage, the life expectancies for each
group differ, thereby influencing the cumulative risk.
Table 1. Life
Expectancy in Years by Age, Race, and Sex
|
Age |
Caucasian Male |
African-American Male |
Caucasian Woman |
African-American Woman |
|
0 |
73 |
65 |
80 |
74 |
|
15 |
59 |
51 |
65 |
60 |
|
25 |
50 |
43 |
56 |
50 |
|
35 |
40 |
34 |
46 |
41 |
|
45 |
31 |
26 |
36 |
32 |
|
55 |
23 |
19 |
27 |
24 |
|
65 |
15 |
13 |
19 |
17 |
|
75 |
10 |
9 |
12 |
11 |
|
85 |
5 |
5 |
6 |
6 |
Table 2. Risk of
Hemorrhage
|
Expected No. of Yr to Live |
Risk of Bleed (%) (2% / yr) |
Risk of Bleed (%) (3% / yr) |
Risk of Bleed (%) (4% / yr) |
|
5 |
10 |
14 |
18 |
|
10 |
18 |
26 |
34 |
|
20 |
33 |
46 |
56 |
|
30 |
46 |
60 |
71 |
|
40 |
55 |
70 |
80 |
|
50 |
64 |
78 |
87 |
|
60 |
70 |
84 |
91 |
|
70 |
76 |
88 |
94 |
|
80 |
80 |
91 |
96 |
Tables
borrowed from Theodore, N., Apostolides, P.J., & Spetzler, R.F. (1996).
Simple risk predictions for arteriovenous malformation hemorrhage.
Neurosurgery,
38(5),
1066-67.
The role of heredity in AVMs is unclear. Patients with a family history of subarachnoid hemorrhage have significantly higher risk of cerebral aneurysms (Nakagawa, Hashi, Kurokawa, & Yamamura, 1999), but occurrences of familial AVMs are rare. On the other hand, familial AVMs found at a young age tend to be multiple, indicating that some genetic factor may predispose these children to have AVMs (Amin-Hanjani, et al., 1998). In order to determine whether there is some hereditary component to AVMs, studies need to be done to scan asymptomatic relatives for undiagnosed AVMs. Back to top.
References
1) (1997). Arteriovenous Malformations. Clinical Presentation and Natural History. http://mcns10.med.nyu.edu/vascular/avm2.html (2000, April 8).
2) Dembo, M. (1982). Arteriovenous malformations of the brain: A Review of the literature since 1960. Archives of Physical Medicine and Rehabilitation, 63(11), 565-568.
3) Toole, J.F. (1990). Cerebrovascular Disorders (4th ed.). New York: Raven Press.
4) Kondziolka, D., McLaughlin, M.R., & Kestle, J.R. (1995). Simple risk predictions for arteriovenous malformation hemorrhage. Neurosurgery, 37(5), 851-5.