There is not a strong correlation between serum valproic acid levels and antimanic effects, but levels in the range of 50 to 150 μg/mL generally are required for therapeutic effect.
Neuropsychiatric adverse effects of valproic acid
With most antiepileptic drugs, adverse effects mainly are dose-related and include sedation, drowsiness, incoordination, nausea, and fatigue. Careful dose titration can reduce the risk of these adverse effects. Research on mothers with epilepsy has shown an association between valproic acid exposure in utero and lower IQ and a higher prevalence of autism spectrum disorder in children.21
Adverse effects on cognitive functioning are infrequent; valproic acid improves cognition in select patients.22 In a 20-week randomized, observer-blinded, parallel-group trial, adding valproic acid to carbamazepine resulted in improvement in short-term verbal memory.23 In a group of geriatric patients (mean age 77 years), no adverse cognitive effects were observed with valproic acid use.24
Masmoudi et al25 evaluated dementia and extrapyramidal symptoms associated with long-term valproic acid use. Among the side effects attributed to valproic acid, parkinsonian syndromes and cognitive impairment were not commonly reported. In a prospective study, Armon et al26 found several abnormal symptoms and signs related to motor and cognitive function impairment in patients on long-term valproic acid therapy. These side effects might be related to a disturbance in the GABAergic pathways in the basal ganglia system. Note that Δ2-valproic acid, a metabolite of valproic acid, preferentially accumulates in select areas of the brain: the substantia nigra, superior and inferior colliculus, hippocampus, and medulla.
What is the next best step in management?
a) surgically implant a shunt
b) adjust the dosage of valproic acid
c) switch to monotherapy
d) switch to an alternative psychotropic medication
e) provide observation and follow-up
The authors’ observations
Unusual appearances of NPH symptoms could hinder early diagnosis and proper treatment. Mr. X was taking valproic acid and venlafaxine for bipolar depression, without any complaints, and was asymptomatic for 8 years—until he developed symptoms of NPH.
In patients who have what can be considered classic symptoms of NPH and are taking valproic acid, consider discontinuing the drug on a trial basis before resorting to a more invasive procedure. This strategy could significantly reduce the cost of health care and contribute to the overall well-being of the patient.
NPH associated with chronic valproic acid use is rare, supported by only 1 case report13 in our literature review. Based on the severity of symptoms and chance for misdiagnosis, it is essential to identify such cases and differentiate them from others with underlying neuropathology or a secondary cause, such as age-related dementia or Parkinson’s disease, to avoid the burden of unnecessary diagnostic testing on the patient and physician.
Family history also is important in cases presenting with sensorineural hearing loss,13 which follows a pattern of maternal inheritance. Consider genetic testing in such cases.
Earlier diagnosis of valproic acid-induced NPH enables specific interventions and treatment. Treatment of NPH includes one of several forms of shunting and appropriate neuroleptic therapy for behavioral symptoms. Although there is a significant risk (40% to 50%) of psychiatric and behavioral symptoms as a shunt-related complication, as many as 60% of operated patients showed objective improvement. This makes the diagnosis of NPH, and referral for appropriate surgical treatment of NPH, an important challenge to the psychiatrist.27
OUTCOME No reemergence
Findings on a repeat MRI 2.5 months after the CSF tap remain unchanged. Surgery is cancelled and medications are discontinued. Mr. X is advised to continue outpatient follow-up for monitoring of re-emerging symptoms of bipolar depression.
At a follow-up visit, Mr. X’s condition has returned to baseline. He ambulates spontaneously and responds to questions without evidence of cognitive deficit. He no longer is incontinent.
Follow-up MRI is performed and indicated normal results.
Neuropsychological testing is deemed unnecessary because Mr. X has fully recovered from cognitive clouding (and there would be no baseline results against which to compare current findings). Based on the medication history, the team concludes that prolonged use of valproic acid may have led to development of signs and symptoms of an NPH-like syndrome.
The authors’ observations
Awareness of an association of NPH with neuropsychiatric changes is important for clinical psychiatrists because early assessment and appropriate intervention can prevent associated long-term complications. Valproic acid is considered a relatively safe medication with few neurologic side effects, but the association of an NPH-like syndrome with chronic valproic acid use, documented in this case report, emphasizes the importance of studying long-term consequences of using valproic acid in geriatric patients. More such case reports need to be evaluated to study the association of neuropsychiatric complications with chronic valproic use in the geriatric population.