Agenesis of internal carotid artery associated with symptomatic partial epilepsy

An 8-year-old Chinese girl had a first episode of symptomatic partial epilepsy at age 2 years. Despite regular treatment with antiepileptic drugs (AEDs), the seizures remitted and exacerbated. Epileptiform EEG discharges were evident, arising from the left centroparietal region. Magnetic resonance imaging (MRI) and computed tomography (CT) scan of the temporal bone and cerebral angiography demonstrated absence of the left internal carotid artery and ipsilateral bony carotid canal. Perfusion brain single photon emission CT (SPECT) with [99mTc] HMPAO showed a perfusion defect at the left posterior temporoparietal lobe. Brain ischemia due to agenesis of the left internal carotid artery (ICA) was speculated as the cause of the partial epilepsy.

Hemimegalencephaly treated by hemispherectomy: report of two cases

Hemimegalencephaly is a rare congenital anomaly of the brain characterized by unilateral hypertrophy, usually with an abnormal gyri pattern and derangement of the cortical architecture. We report 2 patients with hemimegalencephaly who presented with early-onset seizures, hemiparesis and developmental delay. An electroencephalogram showed hemispheric continuous spikes and spike-and-waves in one patient and repetitive spike-and-waves in the other. Magnetic resonance imaging showed left hemimegalencephaly in both cases and in case 1 pachygyria and heterotopia. A functional hemispherectomy was done on case 1 at the age of 33 months and on case 2 at 7 months due to difficulty in seizure control with antiepileptic drugs. The frequency of seizure dramatically decreased and there was an obvious improvement in neurologic development after surgical intervention. Pathology revealed disorganized lamination of the cortical layers with increased neuron size and bizarre-shaped neurons in both cases. Heterotopia of neurons and glia in the subarachnoid space was noted in case 1. Hemispherectomy should be performed as soon as possible when medical treatment fails to control seizures.

Immunocytochemical studies on desmin and vimentin in neuromuscular disorders

Desmin and vimentin are two intermediate filaments, abundant in fetal skeletal muscle, almost undetectable in mature skeletal muscle which increase in regenerating and partially damaged skeletal muscle fibers. To determine their content in neuromuscular disorders immunohistochemical studies of desmin and vimentin were performed on 53 human muscle specimens. The labelled streptavidin biotin technique (DAKO, LSAB Kit, alkaline phosphatase) was used. Strong staining intensity was seen in regenerating and partially damaged fibers of inflammatory myopathies and muscular dystrophy. Necrotic fibers lost their reactivity for both filaments. Type II glycogenosis showed an increased reactivity for desmin and vimentin. A mild increase in desmin and vimentin staining intensity was observed in the atrophic cells of spinal muscular atrophy, but not in the atrophic fibers from other disease entities. Weaker reactivity for desmin was noted in atrophic cells of myotonic dystrophy. The immunohistochemical study of desmin and vimentin in neuromuscular disorders is helpful in detecting degeneration, or regeneration changes, of muscle fibers and may provide clues to the pathogenesis of various muscular disorders.

Etiological classification of chronic headache in children and their electroencephalographic features

Classification and electroencephalographic studies were based on 215 children with chronic headache ranged in age from 3 to 16 years (9.53 +/- 2.86 years old) who were referred to the Pediatric Neurology Clinics of National Taiwan University Hospital due to chronic or severe headache from December 1989 to December 1992. The most common type of headache was seizure headache which constituted 27.0% of all these cases. Migraine headache accounted for 22.3%. The abnormal and borderline electroencephalogram (EEG) rate in seizure headache patients were 75.9% and 24.1% respectively. Comparing the results of migraine patients were 8.3% and 8.3% respectively. Seven cases have been diagnosed as orthostatic dysregulation clinically. All of them presented normal EEG. The response of seizure headache to anticonvulsants was good in the patients with abnormal (87.9%) and borderline EEG (55.6%). We conclude that seizure headache is not uncommon in children and it responses good to anticonvulsants.

Precocious puberty in a case with probable Angelman syndrome

The authors report a 9-year-old girl with mid-facial hypoplasia, maxillary hypoplasia, prognathia, microbrachycephaly, mouth opening and protruding tongue. She also had psychomotor retardation such as mental retardation and speech delay. Frequent laughter fits and seizure disorder was also noted. Although the high resolution chromosome study failed to demonstrate any deletion of chromosome 15q, the clinical picture was compatible with Angelman syndrome. Breast development at the age of six and rapid progression of bone age was noted at follow up. After a series of examinations, the diagnosis of gonadotropin-dependent precocious puberty was made. MRI of brain revealed an intermediate cyst in the pituitary gland and slightly enlarged pineal gland. However, serum alpha-fetoprotein and beta-HCG were undetectable and the size of the pineal gland remained the same at the 1-year follow-up. She was treated with long-acting GnRH analogue and valproic acid. The combination of precocious puberty and Angelman syndrome has not been reported before and such association needs further experience for clarification.

Effects of ethanol on pharmacokinetics and intestinal absorption of paraquat in animals

The effect of ethanol on pharmacokinetics of paraquat was studied in rabbits by intravenous (i.v.) bolus injection of ethanol 0.5 g/kg (or normal saline, in the control group) followed by an i.v. dose of paraquat 20 mg/kg. A greater apparent volume of distribution (Vd), faster distribution rate constants and lower peak plasma concentration (P < 0.01) of paraquat were observed in the ethanol-treated than that in the control rabbits. The total clearance of paraquat was not significantly different between the two groups. The effect of ethanol on the intestinal absorption of paraquat was estimated by in situ intestinal perfusion technique in rats. The perfusate contained paraquat 50 micrograms/ml alone or with 1% or 2% ethanol. Inulin 320 micrograms/ml was added to the perfusate for the measurement of water net flux. The absorption clearance of paraquat as well as the absorption of water increased (P < 0.01) about two-fold in the presence of ethanol. The results of this study suggest that ethanol may potentiate paraquat toxicity by increasing intestinal absorption and tissue distribution. The critical lethal plasma concentration of paraquat is supposed to be lower in the presence of ethanol owing to increased volume of distribution.

Guillain-Barré syndrome in children: a cooperative study in Taiwan

Seventy-two children with Guillain-Barré syndrome (GBS), diagnosed at 11 major teaching hospitals in Taiwan during the period 1986-1990, were studied retrospectively. There were 44 males and 28 females ranging in age from 7 months to 15 years. Preceding events could be traced in 61 patients (85%), including antecedent infection in 59 patients and previous vaccination in 2. As well as the consistent pictures of progressive weakness and generalized hyporeflexia, there were sensory complaints (26%), cranial nerve lesions (46%), respiratory failure (14%) and autonomic dysfunction (25%). Motor symptoms reached a maximum within 20 days in 88% of the patients, with the plateau lasting less than 2 weeks in 75%, and became stable within 3 months in 76%. Overall outcome showed complete recovery in 73% of the patients within 6 months after onset. Four (5.6%) had recurrence, and there was no mortality. The present study revealed that the annual incidence of GBS in Taiwan can be estimated roughly as 0.66 per 100,000 and that the course of childhood GBS is relatively benign.

Hypomelanosis of Ito associated with West syndrome: report of a case

Hypomelanosis of Ito (HI) is a rare neurocutaneous disorder characterized by hypopigmented macules along the Blaschko line and multiple abnormalities, including seizures, developmental retardation, ophthalmologic defects, and chromosome mosaicism. We report a four-month-old female baby with typical skin lesions on the right upper limb, chest, and scalp, noted at the age of one week. She also had a seizure disorder which manifested as neck flexion and hand gripping with series formation from the age of three months. Electroencephalogram (EEG) demonstrated modified hypsarrhythmia. The characteristic clinical and electroencephalographic features favored the diagnosis of West syndrome. Magnetic resonance imaging revealed an absence of abnormal neuronal migration. The auditory brainstem evoked response, nerve conduction velocity, and ophthalmologic examinations were all within normal limits. The seizure responded to adrenocorticotropic hormone therapy on the 12th day of initial therapy, and the EEG became normal. However, another different pattern of seizures characterized by staring and lateral gaze in a right upward direction occurred two weeks later. Carbamazepine and phenobarbital were added to the therapeutic regimen. She was regularly followed up at the outpatient department every two weeks after one-and-a-half months of hospitalization. Infantile spasms with evidence of hypsarrhythmias in the EEG recurred at seven months of age. Oral steroid therapy reduced seizure frequency by 80%. As far as we know, this is the first case report of HI combined with infantile spasms in Taiwan.

Hereditary progressive dystonia with marked diurnal fluctuation (Segawa syndrome) in Taiwan

Since 1988, we have diagnosed 6 cases of hereditary progressive dystonia with marked diurnal fluctuation (HPD) in Taiwan. All cases presented with clinical features similar to those described by Segawa. They consisted of four sporadic and two familial cases. The age at onset ranged from 18 months to 8 years. There is a female predominance of 4:2. All of them showed mild postural tremor and postural dystonia manifested initially by flexion-inversion of a foot. However, unlike Segawa's description, side preference to the right (4:2) was noticed. Neck and axial muscles were not or were minimally involved, except a case presenting with retrocollis and tilting of the neck. These symptoms showed remarkable diurnal fluctuation which became aggravated towards the evening and alleviated in the morning or after rest. Response to L-dopa was dramatic, independent of the duration of illness, and no adverse effect of L-dopa has been observed. Our experience suggested that 10 mg/kg/day of L-dopa may be an optimally effective dose for treatment of patients with HPD. Neurophysiological, neuroradiological and biochemical studies were all normal except in one case who showed prolonged somatosensory potential latencies and white matter changes on MRI. Change of dopamine and its metabolites in CSF, plasma and urine had been investigated in one case.

Acute hemiplegia in infancy and childhood

From 1982 to 1991, there were 57 patients diagnosed with various intracranial disorders manifested initially with acute hemiplegia at the Department of Pediatrics, National Taiwan University Hospital. There were 33 boys and 24 girls, aged 12 days to 18 years old. In etiological consideration, cerebrovascular disease (66.7%), intracranial tumors (12.3%) and head trauma (10.5%) accounted for most of the cases. Besides acute hemiplegia, cranial nerve palsy (47.4%), disturbed consciousness (42.1%), headache (42.1%), vomiting (31.6%), focal seizure (21.1%) and fever (21.1%) were also common manifestations. Neuroimage studies of CT/MRI scan and angiography were the most useful diagnostic tools. Treatment modalities included medical treatment in 25 patients and surgical intervention in 16 patients and supportive treatment in the others. There were 12 fatal cases, half of whom died directly of intracranial pathology. The survivors exhibited various neurological deficits, in which motor deficits, mental retardation, and subsequent seizures were the three most common sequelae.

Rupture of thoracic aortic aneurysm into the lung with formation of pseudoaneurysm: diagnosis and treatment

Three patients with rupture of thoracic aortic aneurysm into the lung with formation of pseudoaneurysm were admitted to our hospital in 1991, of whom, 2 had ascending aortic aneurysms which ruptured into the right upper pulmonary lobe, and another one had descending aortic aneurysm rupturing into the left upper lobe. All 3 cases were misdiagnosed as having pulmonary carcinoma or mediastinal tumor by the other hospital as well as by us. Correct diagnosis was made by aortography or at exploratory thoracotomy. Our preliminary experiences in the diagnosis and treatment of the disease are presented in this paper.

Multicystic encephalomalacia in a surviving monochorionic twin

From a recent monochorionic diamniotic twin pregnancy seen at this hospital, one of the twins died in utero at 37 weeks' gestation. The other twin, a male infant, was delivered by Cesarean section because of fetal distress, with resuscitation performed in the delivery room. The infant developed generalized tonic seizure shortly after stabilization, and was put on anticonvulsants. The initial brain echography was normal; follow-up echograms and CT scans performed at 8 and 12 days old, respectively, revealed diffuse low density over both side of cerebral hemisphere. At one month old, the infants's brain echogram showed diffuse cystic encephalomalacia. At four months, he was noted to be spastic and significantly delayed in neurodevelopment. Disseminated intravascular coagulation caused by fetal-to-fetal transfer of thromboplastic material from the dead fetus was considered as the most possible cause of the neurological complication in this patient. In addition, perinatal hypoxic-ischemic insult may also have been a superimposed, influencing factor.

Nonlinear elimination and hepatic concentration of conjugation-metabolite of valproate in guinea-pigs

The plasma clearance and metabolic rate characteristics of valproic acid (VPA) were studied using guinea-pigs placed on various (0.08-9 mumol ml-1 = 11-1303 micrograms ml-1) steady-state plasma concentrations (Css) by constant intravenous (i.v.) infusion. The total clearance (CL) was significantly decreased at plasma concentration of 0.61 mumol ml-1 (88 micrograms ml-1). The metabolic clearance of VPA was apparently biphasic. The maximum metabolic rate (Vmax) and the Michaelis-Menten constant (Km) for the primary (Vmax1, Km1) and the secondary (Vmax2, Km2) pathways were Vmax1 = 1.52 mumol min-1 kg-1, Km1 = 0.15 mumol ml-1, Vmax2 = 24.98 mumol min-1 kg-1 and Km2 = 11.70 mumol ml-1, respectively. The Km1 value was within clinical therapeutic concentration range. The formation of conjugated VPA (cjVPA) metabolite in liver was shown to be saturable. Plasma protein binding of VPA was also nonlinear. The dose-dependent decrease in metabolic clearance was counterbalanced by the increased unbound fraction (fu), resulting in a relatively constant apparent clearance of VPA over a wide concentration range. The hepatic concentration of VPA was not significantly different from the plasma unbound concentration, again over a wide concentration range. The biliary and hepatic concentrations of VPA were not significantly different; but the concentration ratio of cjVPA in bile compared with that of VPA in liver decreased against hepatic concentration of VPA, which suggests a saturable conjugation rate. The Km value estimated from hepatic cjVPA production as a function of plasma VPA concentration was comparable with the Km1 value.(ABSTRACT TRUNCATED AT 250 WORDS)

Rigid spine syndrome presenting with respiratory failure--report of one case

A case of rigid spine syndrome presenting with respiratory failure was reported. A seven-year-old girl had had dyspnea and orthopnea for one month. Symptoms had aggravated gradually and she was in a state of respiratory failure on arrival at our hospital. There was no evidence of active lung lesions and response to mechanical ventilation was good. Physical examination revealed an extremely thin girl with marked flexion limitation of neck and severe wasting of sternocleidomastoid and intercostal muscles. Serum creatine phosphokinase was moderately elevated (801 IU/L). Muscle biopsy specimen obtained from the right quadriceps femoris revealed increased perimyseal connective tissue and marked Type II fiber atrophy. Electromyography of left paraspinal muscles demonstrated small amplitude, short duration motor unit potentials. She received tracheostomy and a home-care ventilator use during sleep. Ventilatory insufficiency, though rare, should be anticipated in patients with rigid spine syndrome, and timely ventilatory support should be given.

Dose-dependent inhibition in plasma protein binding of valproic acid during continued treatment in guinea-pigs

Plasma protein binding of valproic acid over a wide range of steady-state plasma concentration (11.3 +/- 2.6-1303.0 +/- 122.9 micrograms mL-1: s.e.m., n = 5) in guinea-pigs has been studied. Valproic acid was given by intravenous constant infusion. At steady-state the plasma protein binding of valproic acid was analysed. Nonlinear binding was observed. Unbound fraction (fu) of valproic acid increased from 25 to 95% with the increase of steady-state plasma concentration (Css). The plasma protein-bound drug concentration (Cb) of valproic acid increased initially with Css but decreased after the Css exceeded 345.0 micrograms mL-1, where the Cb was 152.5 +/- 26.8 micrograms mL-1. At a Css of 1303.3 +/- 122.9 micrograms mL-1 the Cb was significantly (P less than 0.05) decreased to 72.8 +/- 20.2 micrograms mL-1. Binding characteristics of valproic acid in-vitro were studied using drug-free guinea-pig plasma with added valproic acid (10-1000 micrograms mL-1). The binding behaviour was also nonlinear in-vitro. The fu increased from 14 to 79% with the increase of valproate concentrations. No decrease in Cb was observed throughout the range. The study demonstrated that binding characteristics of valproic acid in-vivo and in-vitro are not parallel. The results suggest that valproic acid may produce or induce plasma protein binding competitors; metabolites of valproic acid may be implicated.

An experimental study of trachea anastomosis in rabbits using carbon dioxide laser

A technique of sutureless trachea anastomosis in rabbits using carbon dioxide laser was reported herein. In 6 rabbits with laser-assisted trachea anastomoses, only one was found to have slight anastomotic stenosis after operation, whereas 6 rabbits with conventional sutures all were found to have anastomotic stenosis. Results show that laser-assisted trachea anastomosis has certain advantages over the conventional suturing technique, thereby finding wide application in clinical tracheal reconstruction and lung transplantation.

Surgical treatment of double-chamber right ventricle and its associated anomalies

A report on the results of surgical treatment of 5 cases of DCRV and its associated anomaly was presented in this paper. No definite diagnosis of DCRV was made prior to operation. It was found that 2 cases had DCRV as an isolated anomaly, another 2 had the disease associated with VSD, and the remaining 1 had DCRV with right ventricle to left atrium cannulation. Muscular membrane septum type was found in 3 cases, and muscular bundle type in 2.4 cases diagnosed as having DCRV or DCRV with other heart anomalies during operation were treated properly and discharged fully recovered. 1 case died of acute heart insufficiency. Pathologic anatomy and physiology, associated anomalies of DCRV, and some experience with the operative approach were discussed in this article.

Urinary N-acetyl-beta-glucosaminidase (NAG) in children receiving antiepileptic drugs

The activity of urinary N-acetyl-beta-glucosaminidase (NAG) was measured in random urines using the ratio (NAG index) of NAG to grams of urine creatinine in 102 epileptic children taking antiepileptic drugs (AEDs). A high urinary NAG index (2 SD or more above the mean for the age-matched control/normal subjects) was detected in 40 (39%, 40/102) epileptic children with AEDs. None of the 40 epileptic children with abnormal urinary NAG excretion had significant proteinuria. Among the 83 epileptic children under monotherapy, 29 cases (35%) had elevated urinary NAG excretion. Valproic acid presented the highest incidence of abnormal urinary NAG index (78%, 7/9 cases) within the monotherapy group, and the incidence was statistically significantly higher than that (26%, 14/55) in the carbamazepine group (p < 0.005). In the monotherapy group, no significant difference in serum levels of AEDs was found between children with normal urinary NAG excretion and those with abnormal. Nineteen epileptic children were treated with more than one AEDs. Eleven of them (58%, 11/19 cases) had a high urinary NAG index. The incidence of high urinary NAG index in the polytherapy group and that in monotherapy group was not significantly different (p > 0.05). This study suggests that AEDs may be potentially nephrotoxic and that urinary NAG may play a role in screening renal tubular injury in epileptic children under therapy of AEDs. Further investigation should be conducted to determine whether the effect of AEDs on renal tubular cells is or is not reversible.

Marinesco-Sjögren syndrome: report of one case

A three-year-old Taiwanese boy with Marinesco-Sjögren syndrome is reported. Psychomotor retardation had been noticed since early infancy with hypotonia, muscle weakness, delayed motor milestones and imbalance in sitting and standing. Bilateral visual impairment proved to be congenital cataract. Speech was limited to a few words. The parents were consanguineous, and there are two similarly affected siblings. The brain computed tomography revealed cerebellar atrophy. The evoked potential studies indicated a central origin or brainstem lesion. The histopathologic study of the muscle showed variation in fiber size and regenerating fibers. The patient received intraocular lens implantation and was discharged under a home rehabilitation program.

Electroencephalographic and clinical features of typical absence seizures in children

From July 1986 to July 1991, seventeen typical absence seizures, in patients aged 3 to 12 years (mean: 7 years 1 month), were collected for clinical and electroencephalographic (EEG) analysis. All were first-evaluated patients at the Pediatric Neurology Clinic, National Taiwan University Hospital with thorough EEG examination (including waking and natural sleep records) and detailed medical records. All had no history of any brain insult, except for one who had had febrile convulsion before. There were nine female and eight male patients. All had regular bilaterally synchronous and symmetric 3 Hz spike-and-wave discharges and absences. Nine of the 17 cases had interictal focal spike discharges, located over centro-temporal area in 4 cases, fronto-central area in 2 cases and parietooccipital area in the other 2 cases. Another patient was found to have 3 Hz posterior slow waves. Four of the 17 cases had automatisms. Only one case had photo-paroxysmal response. Hyperventilation could induce clinical spells and typical EEG findings in all 17. Normal interictal background activity on the EEG was also found in all cases.

A study of genetic leukodystrophies in Chinese children

During 1986 and 1991, we had diagnosed 12 cases with genetic leukodystrophy including 9 cases with metachromatic leukodystrophy (MLD), 1 case with globoid cell leukodystrophy (GLD, Krabbe's disease), 1 case with neonatal adrenoleukodystrophy (NALD), and the other with probable Pelizaeus-Merzbacher disease (P-M disease). The clinical, biochemical, neurophysiological and neuroradiological features were reported. The diagnosis of MLD, GLD, NALD was confirmed by means of the measurement of serum arylsulfatase A activity, leukocyte galactocerebrosidase activity and serum very long chain fatty acids, respectively. The P-M disease was highly suspected according to clinical picture and evoked potential findings. All the brainstem auditary evoked potentials (BAEPs) and the scalp somatosensory evoked potentials (scalp SEPs) studies in 6 patients with MLD, 1 patient with GLD and 1 patient with NALD were abnormal. In patients with MLD or GLD, the nerve conduction velocity (NCV) studies showed moderate to severe slowing suggesting peripheral demyelinating neuropathy. Brain CT in patients with MLD or NALD demonstrated marked lucency in the white matter. Brain CTs in the patient with GLD showed progressive brain atrophy. In conclusion, though final diagnosis of genetic leukodystrophy should be established throughout biochemical studies, the neurophysiological and neuroimaging studies are of value as an aid to early diagnosis, prediction of clinical course and evaluation of prognosis for genetic leukodystrophy.

Analysis and clinical correlates of the 14 and 6 Hz positive electroencephalographic spikes in Chinese children

From January 1987 to March 1991, electroencephalographic (EEG) analysis and clinical correlates of the 14 and 6 Hz positive spikes were studied retrospectively in 2,026 Chinese patients, ranging in age from 1 to 18 years. All of them were the first-evaluation patients of Pediatric Neurology Clinics, National Taiwan University Hospital, each had had through EEG examinations (including waking and natural sleep records) and detailed medical records. The major findings of the present study are: (1) The overall incidence of the 14 and 6 Hz positive spikes in the series was 2.52% (51/2,026), and that in the age subgroup 1-5 years was significantly lower than those in the subgroups 6-10 years (p less than 0.0001) and 11-15 years (p less than 0.01). (2) 38 out of 51 cases (74.5%) with 14 and 6 Hz positive spikes presented normal EEG background activity. (3) 7 out of 51 cases (13.7%) had coincided negative spikes in frontal areas, and 12 out of 51 cases (23.5%) were associated with other focal or generalized paroxysmal discharges. (4) From the analysis of the clinical manifestations in the 51 cases with the 14 and 6 Hz positive spikes, the episodic attacks of headache, abdominal pain or other autonomic symptoms were most common (49%, 25/51 cases). Of the 25 cases, 19 cases (37.2%, 19/51 cases) were finally diagnosed as autonomic seizure or abdominal epilepsy and 3 cases were diagnosed as migraine. 3 of 10 cases with convulsive seizure or complex partial seizure were associated with autonomic symptom. (5) The etiology in 36 out of 51 cases (70.6%) remained unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

The Rett and Rett-like syndromes: a broad concept

Eight patients who satisfied the following three criteria: 1) autistic behavior, 2) mental retardation and 3) stereotypic hand movements were evaluated. Four patients fulfilled the diagnostic criteria for the Rett syndrome developed by representatives of the International Rett Syndrome Association and the Center for Disease Control, Atlanta, USA. The other four Rett-like patients were atypical in the sense that the manifestations were incomplete or psychomotor development throughout the first 6 months of life was abnormal or the disease was heralded by infantile spasms with transient stereotypic hand movements or the baby was born with congenital microcephaly. All eight patients were girls. No laboratory test result specific for the Rett syndrome or Rett-like syndrome was obtained.

Pharmacokinetics of valproic acid in guinea-pigs with biliary abnormality

To explore whether biliary cannulation, biliary obstruction or gall bladder obstruction could alter the disposition of valproic acid, guinea-pigs were subjected to common bile duct cannulation or ligation, gall bladder-neck ligation or sham surgery as a control. They were then given an intravenous (i.v.) dose of sodium valproate (50 mg kg-1) and the pharmacokinetics of valproic acid in each group were compared. In the cannulated group, significant decreases (P less than 0.05) in the area under the elimination curve (AUC), the volume of distribution at steady-state (Vdss) and the mean residence time (MRT) were observed. Significant increases (P less than 0.05) in the elimination rate constant (kz) and total clearance (CLtot) of valproic acid were noted. In the biliary obstructed guinea-pigs, the Vdss was significantly decreased (P less than 0.05). In the gall bladder obstructed guinea-pigs, there was a secondary peak of valproate plasma concentration, and the kz was significantly decreased. The biliary excretion of unchanged and conjugated valproic acid was 2.0 +/- 0.7 (s.e.m.) and 19.7 +/- 3.6 (s.e.m.)% of dose, respectively, and was almost completely reabsorbed in the enterohepatic recycling. Urinary excretion of unchanged and conjugated valproic acid, as well as non-conjugate metabolic clearance of valproic acid, were not significantly different among the four groups. The results suggest that the pharmacokinetics of valproic acid in guinea-pigs are particularly sensitive to interruption of the enterohepatic cycle. Biliary obstruction may elevate plasma concentrations owing to the decreased Vdss of valproic acid. Gall bladder obstruction may cause fluctuation of valproate plasma concentrations. The data indicate that the apparent total clearance of valproic acid is significantly less than the intrinsic clearance owing to enterohepatic recycling.