Studies on Dilantin intoxication. I. Ultrastructural analogies with the lipoidoses

Can Therapeutic-Range Chronic Phenytoin Administration Cause Cerebellar Ataxia?

Phenytoin (PHT) is a first line antiepileptic drug (AED) used to treat many epilepsy syndromes. As with other AEDs, there are various adverse effects associated with PHT. For this brief review, we searched for evidence of cerebellar ataxia as a chronic adverse effect of therapeutic-range PHT treatment. Many previous studies appeared related to this issue, but many of those studies were designed to resolve questions related to the persistent residual effects of toxic-range PHT therapy, or they were inconclusive due to an absence of critical information such as PHT serum concentration, cerebellar symptoms/signs, and other factors contributing to cerebellar degeneration. Nevertheless, there were a few reports suggesting that cerebellar ataxia may be a chronic adverse effect of therapeutic-range PHT therapy and that a possible pathomechanism for that effect is folate deficiency. Moreover, there is the possibility that there may be patient-specific susceptibility factors affecting ataxia. Further studies are needed to elucidate the incidence, risk factors, and pathomechanism of cerebellar ataxia as a chronic adverse effect of therapeutic-range PHT treatment.

Deformation-based morphometry of prospective neurodevelopmental changes in new onset paediatric epilepsy

Epilepsy is a prevalent childhood neurological disorder, but there are few prospective quantitative magnetic resonance imaging studies examining patterns of brain development compared to healthy controls. Controlled prospective investigations initiated at or near epilepsy onset would best characterize the nature, timing and course of neuroimaging abnormalities in paediatric epilepsy. In this study, we report the results of a deformation-based morphometry technique to examine baseline and 2-year prospective neurodevelopmental brain changes in children with new and recent onset localization-related epilepsies (n = 24) and idiopathic generalized epilepsies (n = 20) compared to healthy controls (n = 36). Children with epilepsy demonstrated differences from controls in baseline grey and white matter volumes suggesting antecedent anomalies in brain development, as well as abnormal patterns of prospective brain development that involved not only slowed white matter expansion, but also abnormalities of cortical grey matter development involving both greater and lesser volume changes compared to controls. Furthermore, abnormal neurodevelopmental changes extended outside the cortex affecting several subcortical structures including thalamus, cerebellum, brainstem and pons. Finally, there were significant differences between the epilepsy syndromes (localization-related epilepsies and idiopathic generalized epilepsies) with the idiopathic generalized epilepsies group showing a more disrupted pattern of brain structure both at baseline and over the 2-year interval.

Cerebellar atrophy in temporal lobe epilepsy

PURPOSE

The goal of this work was to determine the presence and degree of cerebellar atrophy in chronic temporal lobe epilepsy, its clinical seizure correlates, and its association with general cortical atrophy.

METHODS

Study participants were 78 persons with temporal lobe epilepsy and 63 age- and gender-matched healthy controls. All subjects underwent high-resolution MRI with manual tracing of the cerebellum. Clinical seizure features and history were obtained by structured interview and review of medical records.

RESULTS

The epilepsy group exhibited significant abnormality in cerebellar volume, with mean reductions ranging from 4 to 6.6% depending on adjustments. Significantly more individual subjects with epilepsy exhibited cerebellar atrophy compared with controls across all operational definitions or thresholds of abnormality including z < or = -2.0 (13% TLE, 3.4% controls) and z < or = 1.5 (22% TLE, 3.4% controls). Clinical seizure features reflecting both neurodevelopmental (history of initial precipitating injuries) and severity of course (longer duration, increased number of lifetime generalized tonic-clonic seizures) factors were associated with cerebellar atrophy. Atrophy of the cerebellum could be observed independent of more general (cerebral) atrophic processes.

CONCLUSIONS

The presence of cerebellar atrophy is a reflection of the extratemporal abnormalities that can be observed in localization-related temporal lobe epilepsy, which may be due, at least in part, to factors associated with epilepsy chronicity.

Ultrastructure of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in experimental valproate encephalopathy and after valproate withdrawal

The aim of the study was to analyse the astrocyte ultrastructure within the hippocampal gyre cortex and neocortex of the temporal lobe in valproate encephalopathy induced by chronic administration of an anti-epileptic drug - sodium valproate (VPA) to rats for 1, 3, 6, 9 and 12 months, once daily intragastrically, in a dose of 200 mg/kg b.w. and after its withdrawal for 1 and 3 months. Prolonged application of VPA caused damage to protoplasmic astrocytes of the cortex regions examined, mainly in the pyramidal layer, which intensified in the later stages of the experiment, especially after 9 and 12 months. Ultrastructural alterations in astroglia during this experiment did not differ significantly between the hippocampal cortex and neocortex. The most pronounced astroglial abnormalities, concerning about 2/3 of protoplasmic astrocytes after 9 and 12 months, were characterized by considerable swelling of cells, with the presence of empty vacuolar structures in the cytoplasm, a substantial decrease in the number of gliofilaments or even their complete loss, which indicated fibrillopoietic failure of the cell, and the appearance of astrocytes showing phagocytic activity. The astrocytic changes coexisted with distinct damage to neurones and structural elements of the blood-brain barrier. One month after termination of chronic exposure to the drug, the abnormalities did not subside, whereas after 3 months features of distinct normalization could be observed in a considerable number, more than a half, of astrocytes. In valproate encephalopathy, apart from any direct effect of VPA and/or its metabolites on astrocytes, the main cause of the protoplasmic astroglial damage in the cortex of the CNS structures examined could be associated with changes in microcirculation in the cortex (vasogenic factor), leading to its ischaemia.

Ultrastructure of Purkinje cell perikarya and their dendritic processes in the rat cerebellar cortex in experimental encephalopathy induced by chronic application of valproate

Long-term intragastric administration of the antiepileptic drug sodium valproate (Vuprol Polfa) to rats for 1, 3, 6, 9 and 12 months, once daily at the effective dose of 200 mg/kg body weight showed morphological evidence of encephalopathy, manifested by numerous nonspecific changes within Purkinje cell perikarya and their dendritic processes. The first ultrastructural abnormalities appeared after 3 months. They became more severe in animals with longer survival and were most pronounced after 12 months. The changes were maintained both 1 and 3 months after drug withdrawal. Mitochondria of Purkinje cell perikarya were most severely affected. Damage to mitochondria was accompanied by disintegration and fragmentation of granular endoplasmic reticulum, dilation of channels and cisterns of Golgi apparatus, enlargement of smooth endoplasmic reticulum elements including submembranous cisterns, and accumulation of profuse lipofuscin deposits. Frequently, Purkinje cells appeared as dark ischemic neurones, with focally damaged cellular membrane and features of disintegration. Swollen Bergmann's astrocytes were seen among damaged Purkinje cells or at the site of their loss. The general pattern of submicroscopic alterations of Purkinje cell perikarya suggested severe disorders in several intercellular biochemical extents, including inhibition of oxidative phosphorylation and abnormal protein synthesis, both of which could lead to lethal damage. Ultrastructural abnormalities within dendrites were characterized by damage to elements of smooth endoplasmic reticulum, which was considerably enlarged, with formation of large vacuolar structures situated deep in the dendroplasm. Mitochondrial lesions and alterations in cytoskeletal elements--disintegration of microtubules or even their complete loss--were also observed. The general pattern of abnormalities within the organelles and cytoskeletal elements of dendritic processes in Purkinje cells in the VPA chronic experimental model imply that there are disturbances in detoxication processes. Furthermore these changes were irreversible, as they were maintained after drug withdrawal.

Morphological features of encephalopathy after chronic administration of the antiepileptic drug valproate to rats. A transmission electron microscopic study of capillaries in the cerebellar cortex

Long-term intragastric application of the antiepileptic drug sodium valproate (Vupral "Polfa") at the effective dose of 200 mg/kg b. w. once daily to rats for 1, 3, 6, 9 and 12 months revealed neurological disorders indicating cerebellum damage ("valproate encephalopathy"). The first ultrastructural changes in structural elements of the blood-brain-barrier (BBB) in the cerebellar cortex were detectable after 3 months of the experiment. They became more severe in the later months of the experiment, and were most severe after 12 months, located mainly in the molecular layer of the cerebellar cortex. Lesions of the capillary included necrosis of endothelial cells. Organelles of these cells, in particular the mitochondria (increased number and size, distinct degeneration of their matrix and cristae) and Golgi apparatus were altered. Reduced size of capillary lumen and occlusion were caused by swollen endothelial cells which had luminal protrusions and swollen microvilli. Pressure on the vessel wall was produced by enlarged perivascular astrocytic processes. Fragments of necrotic endothelial cells were in the vascular lumens and in these there was loosening and breaking of tight cellular junctions. Damage to the vascular basement lamina was also observed. Damage to the capillary was accompanied by marked damage to neuroglial cells, mainly to perivascular processes of astrocytes. The proliferation of astrocytes (Bergmann's in particular) and occasionally of oligodendrocytes was found. Alterations in the structural elements of the BBB coexisted with marked lesions of neurons of the cerebellum (Purkinje cells are earliest). In electron micrographs both luminal and antiluminal sides of the BBB of the cerebellar cortex had similar lesions. The possible influence of the hepatic damage, mainly hyperammonemia, upon the development of valproate encephalopathy is discussed.

Lipopigment in rat hippocampal and Purkinje neurones after chronic phenytoin administration

The accumulation of lipopigment may indicate ageing, certain diseases and cellular damage, while phenytoin, which has been claimed to cause selective clinical cerebellar dysfunction and degeneration, has been reported to produce increased lipopigment accumulation in rat Purkinje neurones. In the present study, 8 rats received phenytoin, 300 mg/kg/day for 20 weeks, and were compared with a control group of 9 rats in respect of lipopigment in Purkinje and hippocampal neurones. Neuronal lipopigment was identified by fluorescence microscopy. The results did not indicate that phenytoin administration was associated with an increase in the area corresponding to (i.e. within the outlines of) neuronal lipopigment in Purkinje neurones, although the relatively small number of animals limits the power of the study. However, in hippocampal neurones, a two-way analysis of variance for numbers of discrete regions of lipopigment demonstrated a significant interaction (P = 0.003) between, firstly, size categories of discrete regions of lipopigment and, secondly, phenytoin administration or a control procedure. In hippocampal neurones, phenytoin administration was accompanied by a decrease in the numbers of discrete lipopigment regions in the smaller size categories and an increase in the numbers in the larger size categories. This finding indicates the need for further investigation into the effects of phenytoin on brain regions other than the cerebellum, as intellectual deterioration may be related to chronic use of this drug.

Neuronal lipopigment: a marker for cognitive impairment and long-term effects of psychotropic drugs

Lipopigment, identifiable in the fluorescence microscope, is thought to be cellular debris partly derived from free-radical-induced peroxidation of cellular constituents. The volume of neuronal lipopigment has been positively correlated with advancing age, Alzheimer dementia, and the neuronal ceroidoses, while various changes in neuronal lipopigment have been reported in association with the chronic administration of dihydroergotoxine, ethanol, phenytoin, centrophenoxine, and chlorpromazine. An increase in the volume of neuronal lipopigment may indicate increased functional activity of the cell, impaired removal of pigment or anoxia. Chronic administration of agents which can be correlated with decreased neuronal lipopigment in animal models might protect neuronal function against any adverse effects associated with (but not necessarily resulting from) lipopigment accumulation in normal ageing, anoxia, or certain degenerative diseases. Long-term studies of the prophylactic use of such agents, or of drugs which neutralise free radicals, may be indicated. Other clinical applications of such drugs may include protection against the effects of free radicals formed during periods of oxygen deprivation.

A study of cerebellar and cerebral cortical degeneration in miniature poodle pups with emphasis on the ultrastructure of Purkinje cell changes

In a litter of three Miniature Poodles, a normal female pup contrasted with two males which displayed severe equilibrium and postural disturbances soon after birth. In the male pups diffuse cerebral cortical degeneration accompanied cerebellar cortical atrophy, which was characterized by extensive loss and degeneration of Purkinje neurons. As in some prior histological descriptions of canine cerebellar atrophies, degenerating Purkinje cells appeared either pale, swollen and vacuolated or shrunken and hyperchromatic. Swollen vacuolated cell bodies and condensed necrotic neurons were scattered through the cerebral cortex. Ultrastructural studies revealed that the vacuolar degeneration in Purkinje and cerebral neurons was referable to marked dilation of endoplasmic reticulum and loss of ribosomes. In shrunken Purkinje neurons, increased cytoplasmic eosinophilia was associated with a decline in Nissl bodies and accumulations of mitochondria and especially lamellar bodies. The latter, stacked derivatives of endoplasmic reticulum, were not encountered in shrunken cerebral perikarya. Lamellar bodies reached giant proportions in the dendritic stems of degenerating Purkinje neurons. In Purkinje axons, however, these bodies often were overshadowed by aggregates of axoplasmic tubules. The cytological changes in these Poodle pups were notably different from those reported in earlier ultrastructural studies of canine inherited cerebellar degenerations.

Complex partial seizures: cerebellar metabolism

We used positron emission tomography (PET) with [18F]2-deoxyglucose to study cerebellar glucose metabolism (LCMRglu) and the effect of phenytoin (PHT) in 42 patients with complex partial seizures (CPS), and 12 normal controls. Mean +/- SD patient LCMRglu was 6.9 +/- 1.8 mg glucose/100 g/min (left = right), significantly lower than control values of 8.5 +/- 1.8 (left, p less than 0.006), and 8.3 +/- 1.6 (right, p less than 0.02). Only four patients had cerebellar atrophy on CT/MRI; cerebellar LCMRglu in these was 5.5 +/- 1.5 (p = 0.054 vs. total patient sample). Patients with unilateral temporal hypometabolism or EEG foci did not have lateralized cerebellar hypometabolism. Patients receiving phenytoin (PHT) at the time of scan and patients with less than 5 years total PHT exposure had lower LCMRglu, but the differences were not significant. There were weak inverse correlations between PHT level and cerebellar LCMRglu in patients receiving PHT (r = -0.36; 0.05 less than p less than 0.1), as well as between length of illness and LCMRglu (r = -0.22; 0.05 less than p less than 0.1). Patients with complex partial seizures have cerebellar hypometabolism that is bilateral and due only in part to the effect of PHT.

Electron microscopy in the diagnosis of lysosomal storage diseases

Lysosomal storage diseases (LSD) affect cells of the conjunctiva in the absence of clinical eye findings. Consequently conjunctiva was added to skin, rectal mucosa, and peripheral blood lymphocytes as a biopsy site for electron microscopic examination in suspected LSD. The abnormally stored substrates in LSD are the result of diminished lysosomal enzyme activity. Although all cells lack the deficient lysosomal enzyme, the quantity of stored material varies with the extent of breakdown of substrate in the cell under normal circumstances. The stored material does not accumulate in all cells and may have a different cellular morphology at different sites. Although no one tissue provides universally diagnostic material for electron microscopy, skin and conjunctiva are optimal for most LSD. Rectal mucosa and peripheral blood lymphocytes are also useful in many cases. Biochemical assays have replaced brain biopsy for diagnosis but these techniques may give equivocal or non-diagnostic results, and in some diseases the enzyme defect remains undefined. Of the 359 biopsies of conjunctiva, skin, rectal mucosa, and lymphocytes we evaluated for LSD and other neurodegenerative diseases, 65 showed abnormal lysosomal storage; in 41 a specific diagnosis was made by biochemical assay or morphology. Ultrastructural examination of tissue from patients with clinically suspected storage disease may disclose pathognomonic alterations or suggest a differential diagnosis even in the absence of clinically evident involvement of the biopsied tissue. Biopsy has particular value in those diseases with incompletely characterized biochemical abnormalities.

Phenytoin neurotoxicity in developing mouse cerebellum in tissue culture

Phenytoin applied to developing neonatal mouse cerebellar cultures at concentrations of 9-46 micrograms/ml of nutrient medium from the day of explantation to 16 days in vitro induced cerebellar cortical degeneration. The degree of neurotoxicity correlated with drug concentration. Purkinje cells were the most susceptible of the cerebellar elements, and intracerebellar nucleus neurons were the most resistant. In contrast, mature mouse cerebellar explants were resistant to chronic exposure to high concentrations of phenytoin.

Uptake of phenytoin by tissues of Mongolian gerbils

1. Radioactive phenytoin was extracted from brain, cerebellum liver and kidney of i.p. injected Mongolian gerbils that were killed at hourly intervals. 2. The drug was extracted by two procedures. Procedure I involved acidification and chloroform extraction, the other, procedure II, an alkaline extraction, acidification and solubilization in chloroform (II). 3. Procedures I and II yielded 98 and 93% recoveries, respectively, from experiments performed either in vivo or in vitro. 4. Concentrations of labeled phenytoin found in brain, cerebellum, liver and kidney from the first to the fifth hour were 7.7, 7.8, 5.2, 4.0 and 2.2% (I) and 10.6, 8.5, 7.2, 4.0 and 2.8% (II) of the amount injected, correspondingly. 5. Concentrations of phenytoin in cerebellum were greater by a statistically significant margin than were those in other tissue at the third hour following the time of injection of radioactive phenytoin but liver and kidney concentrations were greater than cerebellum uptake at the fourth and fifth hour. 6. Brain showed the lowest incorporation of phenytoin throughout five hours.

Cerebellar degeneration due to chronic phenytoin therapy

Five patients developed cerebellar degeneration while being treated with phenytoin. All had high plasma levels of the drug, and none was having seizures of a type that could have caused systemic hypoxia at the time the cerebellar syndrome appeared. Cerebellar degeneration was confirmed by the finding of atrophy on CT scan and by persistence of cerebellar signs when plasma phenytoin levels were decreased. We suggest that chronic phenytoin therapy can cause cerebellar degeneration. The question of whether phenytoin or the cumulative effect of hypoxia from repeated convulsions causes cerebellar degeneration should not be posed as one of exclusive alternatives, since hypoxia is a well-known cause of cerebellar atrophy. Instead, the question should be whether or not phenytoin can also be responsible. The cases reported here suggest that it can.

Effects of diphenylhydantoin on the spontaneous activity of Purkinje, nucleus interpositus, red nucleus and motor cortex cells

(1) Extracellular multiunit recordings were made of the spontaneous activity in cerebellar Purkinje cells, nucleus interpositus, red nucleus and sensorimotor cortex in acute cat preparations. (2) Changes in this spontaneous neural activity produced by the administration of diphyenylhydantoin (DPH) were studied. DPH was infused i.v., generally at a concentration of 2.5 mg/ml and at a rate varying from 0.08 to 0.48 mg/kg/min. Two different patterns of infusion were used: fixed time, variable rate and variable time, fixed rate. Pulsed doses were also given at intervals of 5--10 min. (3) DPH at a level of 10--20 mg/kg produces a significative initial deceleration in all structures followed by a significative acceleration in the Purkinje cells, nucleus interpositus and red nucleus as a dose of 20--30 mg/kg is reached. Higher levels caused a profound depression of multiunit activity. (4) The activation produced by DPH is oscillatory (3--5/min) in character and is composed of 'trains' which occur at a rate of 20--30/sec with very rapid discharge frequencies (600--800 Hz). (5) A direct significant correlation was found between DPH serum levels and the intravenously administered dose. The activating DPH dose (20--30 mg/kg) corresponded to serum levels of 24--32 micrograms/ml. (6) The possibility is discussed whether the anticonvulsant action of DPH may be due in part to the production of rhythmic oscillatory activity in the cerebello-rubro-olivo-cerebellar ciruit and the depression of the cerebellothalamic-cortical pathway.

Neuropathological changes in cerebellar biopsies of epileptic patients

In 5 patients with pharmacologically intractable epilepsy, biopsy of the cerebellar cortex at the time of surface electrode implantation for therapeutic stimulation demonstrated marked degeneration of the Purkinje cell layer in every case. Two of the patients had never experienced a generalized convulsion. Comparison of these biopsy findings with the autopsy findings in two other groups of patients with a seizure disorder of different duration and severity and with the findings in other reported series suggests that permanent neuronal damage in epilepsy is related to the cumulative effects of the frequency and chronicity of the disorder. The pathogenesis remains unclear. The histopathological changes are identical to those seen in generalized cerebral hypoxia, but the observations in our series support the view that in epilepsy the pathogenesis may not be hypoxic.

Histological observation of the brain of Tay-Sachs disease with seizure and chronic DPH intoxication--report of an autopsy case

The patients was a 3-year-old boy with psychomotor retardation and attacked by seizures since 8 months of age. On funduscopy, the maculla presented a cherry-red spot. Serum hexosaminidase A activities were as low as 8.2 percent. Both parents were carriers. The patient was diagnosed as classical Tay-Sachs disease by neurological examination. Diphenylhydantoin was continuously given for 2 years and 2 months till his death. Autopsy revealed swelling of the cerebrum, atrophy and sclerosis of the cerebellum, hepatomegaly and mild enlargement of the lymph nodes. Histologically, the cerebrum showed ballooned swelling of nerve cells, slight gliosis and demyelination, while cerebellar Purkinje's cells and granular cells were degenerated and disappeared. The cerebellar cortex showed small focal spongy degeneration. By electron microscopy, membranous cytoplasmic bodies were found in the nerve cells. The change of brain observed in this case were interpreted as a combined result of (i) essential change to classical Tay-Sachs disease, (ii) ischemic change due to frequently repeated seizures, (iii) chronic toxicity by long-term anticonvulsant administration.

[Electron microscopic study of nerve, muscle and skin lesions induced by perhexiline maleate (author's transl)]

The pathological findings in four nerves and muscles and in one skin biopsies from four patients treated with perhexiline maleate for angina pectoris are reported. In every case, a muscular denervation atrophy and a decrease in the large diameter myelinated fibers were observed. Only one case showed a decrease of the total number of myelinated fibers, on quantitative studies. The electron microscopic study of each nerve displayed findings consistent with a predominant schwannian degeneration, associated with a few onion bulbs formations and, in two cases, with a mild wallerian degeneration. The most striking finding consisted in the presence of polymorphous membrane-bound inclusions reminding the morphology of lysosomal complex lipids. These structures were very abundant in Schwann cells, but they were seen also in fibrocytes, endothelial and pericytic cells. Similar inclusions were present in the single muscle and skin biopsies studied by electron microscopy. In the muscle, they were seen in muscular cells as well as in endothelial and pericytic cells. In the skin, similar inclusions were observed in endothelial, smooth muscle and sweat gland cells. These inclusions were difficult to identify in one micron thick sections, emphazing the need of ultrastructural study for diagnostic purposes.

Neurotological findings in diphenylhydantoine intoxication

It is well known that diphenylhydantoine (DPH) can cause such side effects as gingivitis, hypertrichosis, ataxia, nystagmus, diplopia and others. Although there are many reports about DPH intoxication, very few papers mention the neurotological aspects of this condition. Three cases of DPH intoxication which manifested neurotological changes were treated. The common remarkable findings of these cases were equilibrium disturbance, gaze nystagmus and the absence and/or irregularity of optokinetic nystagmus (OKN). As other neurotological findings do not show any peripheral labyrinthine lesion, the equilibrium disturbances noticed in our cases probably did not originate from the labyrinth but from the central nervous system (CNS). The precise origin of gaze nystagmus noted in these cases has not yet been clarified. It seems to be evident, however, that this type of gaze nystagmus is not due to a peripheral labyrinthine lesion. It is well known that the inhibition or the disturbance of OKN may be caused by central lesions, but the origin or localization of the dysfunction in the CNS has not yet been clarified. On the other hand, animal experiments and postmortem examination of patients with DPH intoxication reveal that the main histologic lesions are located in the cerebellum, especially in the Purkinje cells. Although the precise localization of the lesions in our cases is not known the relationship between clinical findings and histological findings of DPH intoxication can be emphasized.