Atkinson.qxp 18/7/07 10:45 Page 16
Epilepsy
Figure 2: Common Side Effects Seen in Patients Enrolled in
course of VNS placement has rarely been associated with transient
Trials EO1–EO5
asystole. Rhythm strips from three such patients suggested complete
arteriovenous (AV) block occurring during lead testing.
48
This is a rare
Patients
event, estimated to occur in approximately 0.1% of patients.
49
Some
70%
of these patients were successfully treated with VNS with no
60%
60%
subsequent cardiac complications.
48,50
Importantly, comparison of
50%
sudden unexplained death in epilepsy patients (SUDEP) rates in
patients treated with VNS has been found to be no different from
40%
38% seizure patients without VNS.
51
30%
28%
20%
The most common side effects reported in clinical trials are hoarseness,
21% 21% 3 months
19.3%
12 months voice change or cough associated with stimulation. The rate of
10% 12%
4%
2%
7.8% 8%
5.9% 2.6%
3% 3.2%
24 months
hoarseness or voice alteration in the first two randomised, blinded trials
0%
36 months
was 37.2–66.3% at three months, and coughing in 7.5–45.3% at three
Hoarseness Cough Paresthaesia Dyspnoea
months.
25,27
Importantly, there are no significant cognitive side effects.
Side effects
Compiled data from clinical trials EO1–EO5 looked at side effects at
Patients were followed into the open study portion of the trials with data collected up
12–36 months (see Figure 2). By 12 months only 29% experienced
to three years. Note that the percentage of patients reporting these side effects declined
with time.
hoarseness and 7.8% had cough, indicating possible attenuation of
side effects with time.
36
Ben-Menachem looked at patients as far out as
more than 50%, and 38% had a greater than 75% reduction in seizure five years, and hoarseness was reported in 11 out of 64 patients.
31
frequency. At six months, drop attacks had decreased by 88% and Other commonly reported side effects include dyspnoea, paresthaesias
atypical absence seizures by 81%, and at three months complex partial and pain at surgical site.
25,27,29,31,36
Similar side effects have been found
seizures had decreased by 23%.
43
Prior studies that included LGS in paediatric populations.
3,40–44,46
patients also showed clinical efficacy in children
3,31,41,44,45
and adults.
30
Recently, Majoie et al. evaluated 19 patients with LGS or LGS-like Conclusions
syndromes and found only 21% of patients having greater than 50% VNS has been shown to be efficacious and safe for the treatment of
reduction in total seizures at 24 months.
46
medically intractable partial or generalised epilepsy in adults and
children. Clinical improvement has been demonstrated within three
Vagus Nerve Stimulation Safety months, and efficacy generally continues to rise until a plateau is
VNS has proven to be safe and well tolerated with rare adverse events, reached in the second or third year. The mechanism by which VNS
and generally mild side effects that are usually tolerable without exerts its effect has not yet been clearly defined, but is being actively
cessation of therapy. Infection may complicate surgery. Most of these pursued on many different research fronts. Nearly 10 years after FDA
cases can be simply treated with antibiotics, though rarely device approval, VNS has developed a proven track record for adjunctive
removal is necessary (reviewed in reference 47). Lead testing in the therapy in patients with medically intractable epilepsy. ■
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