GLYCINE ENCEPHALOPATHY

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No complete study dealing with all the aspects of the disorder is available, however, to the exception of a recent paper by one of us (Dalla Bernardina et al. 1978). We report in this work, 4 personal cases of nonketotic hyperglycinemia, together with a review of the literature, to delineate, the clinical, EEG, biochemical and pathologic features of this disorder. unremarkable pregnancy and delivery from non-consanguineous parents. Two brothers had died from a similar, but undiagnosed disorder, within the first 10 days of life. After a free interval of 24 hours, the child became very hypotonic (especially the neck muscles). Within 24 hours the hypotonia increased, obtundation appeared and respiratory difficulties necessitated assisted ventilation. No metabolic acidosis was present and CSF was normal as was a Electroencephalogram at age 2 days (Fig. I), recorded a very depressed basal activity interrupted by pseudoperiodic discharges of slow spike-waves, either synchronous or dissociated in the two hemispheres.
At 3 months the periodic paroxysms had disappeared and the tracing was now hypsarrhythmic.

Case 2
Pil. A., a female born at term after an uncomplicated pregnancy and delivery from non-consanguineous parents. One brother had died at age 5 days from a disorder featuring hypotonia, drowsiness and hyperreflexia with onset at 48 hours of life. A. became hypotonic and unresponsive after a 20-hour free interval. She was lying in the frog position with full lateral rotation of the head. The neurological signs increased during the 2nd day of life and respiratory irregularities were first noted. No metabolic acidosis was noted. Segmental, erratic, myoclonias were almost continuously present from the 3rd day onwards, intermingled with nlassive bilateral ones. Lumbar puncture was normal. A plasma amino-acid determination on the 4th day, showed a massive elevation of glycine level (> 1150 pM/l) and the CSF glycine was 245 ~Ml1. The EEG at age 4 days showed a very depressed basal activity periodically interrupted by high amplitude paroxysmal runs of atypical spike-waves, synchronous or asynchronous over both hemispheres (Fig. 2).
The infant died at 5 days of life. Neuropathological examination was performed after 15 % formaline fixa- tion. Selected fragments of cortex, white matter and basal ganglia were embedded in ~araffin. Sections were stained with hematoxylin-eosin, alcian Blue for myelin study and cresyl violet (Nissl), for photonic microscopy. Fresh brain weight was 420 g (mean for age 358 g). Pathological abnormalities mainly affected the white matter of the hemispheres. The internal capsule, normally myelinized for the age, was the seat of a very marked spongiosis, that gave it the appearance of a loose meshwork, lined by normal remaining myelin sheaths (Fig. 3). A moderate gliosis made of protoplasmic astrocytes was evident. A similar grade of spongiosis, without demyelination was also seen in the putaminocaudal fibers. The lenticular nucleus was intact, to the exception of a few small areas of. perivascular spongiosis. In the thalami, along the 3rd ventricle, the ependyma was desquamated and a sheet of dense gliosis was evident underneath, together with a very marked spongiosis. The rest of the hemispheric white matter, e. g. the centrum semiovale which is not yet myelinated at this age, was only slightly and finely spongiotic and was the seat of a mild fibrillary gliosis. In the frontal, parietal and temporal cortex, the neurones were well preserved but occasional areas of spongiosis were seen in the molecular layer (Fig. 4). The cerebellum was not examined.

Case 3
Tous. C., a male infant, born at term weighing 3900 g from non-consanguineous parents became ill after a free interval of 18 hours. A sister had died at the age of 8 days with an identical clinical picture. Initial signs included marked generalised hypotonia, unresponsiveness and respiratory irregularities, which demanded assisted ventilation at age 4 days. At the same time continuous erratic myoclonias were noted. At age 15 days, respiration was spontaneous, segmental myoclonias were still evident and polymorphous partial seizures had appeared. 'Aminoacid chromatography on day 15 showed very marked hyperglycinemia (1 598 pMI1). No ketosis or metabolic acidosis was present. The baby died at age 2.5 months. The myoclonias and seizures had persisted and tonic axial spasms had started at age 1.5 months. EEG (Fig. 5) at age 8 days showed an almost flat traci'ng with intermittent paroxysmal bursts of atypical spike-waves. At age 16 days, the paroxysmal bursts persisted but the basal activity was now hyperactive. At 30 days, nonreactive multifocal paroxysmal anomalies without periodical bursts were evident. At 45 days, a tracing of atypical hypsarrhythmia was recorded.

Case 4
Sand. T., ( A first EEG at age 30 hours was similar to those of the first three cases at the same age. Progressively, the basal activity became hyperactive while the pseudoperiodic bursts increased in frequency and were sometimes accompagnied by massive myoclonus. Infraclinical, localised EEG discharges became evident (Fig. 6). Later on, the pseudoperiodic discharges disappeared, the tracings were hypsarrhythmic during sleep and numerous spasms were recorded during wakefulness (Fig. 7). From 3 months onwards multifocal paroxysmal activities were recorded (Fig. 8) and, after age 8 months, the tracings became monotonous while partial seizures disappeared. The spasms were then almost continuous but had no electroencephalographic expression. In all 4 cases a stereotyped clinical and EEG picture was observed, made of lethargy, hypotonia, erratic and massive myoclonus, and pseudo-periodic paroxysmal bursts on an almost flat EEG. In surviving patients the course was relentless with progressive hypertonia, partial seizures, repetitive spasms and a hypsarrhythmic EEG, followed by a terminal stage of decerebration with an areactive EEG.

Clinical data
We have been able to find in the literature 61 established cases of nonketotic hyperglycinemia. Eight atypical cases (3 cases of Bank and Morrow 1972, 2 cases of Holmgren and Son Blomquist 1977, cases 1, 2, 5 of Perry et al. 1975) will be considered separately in the discussion, leaving 53 cases for analysis.
In all cases, a stereotyped clinical picture emerged in the neonatal period, following a symptom-free interval of 8 hours to 8 days. Symptoms first appeared during the first 24 hours in 22 patients and during the following day in another 13. Profound hypotonia and lethargy are usually the first sign, progressing to unresponsiveness and coma within a few days. Deep tendon reflexes are normal or increased. Respiratory disturbances (apnea or irregular rhythm) frequently necessitate assisted ventilation. No metabolic acidosis is ever mentioned. Within the first 10 days of life, very frequent seg-mental, asynchronous, erratic myoclonias make their appearance in all patients, usually in association with massive myoclonus. When patients live to more than 20 days (18 out of 53 died before this age), the respiratory troubles disappear and survival of a few months to 15 years is then common. From about 12 months of age, epileptic seizures are frequent and resistant to therapy. These have been reported in 35 of 53 infants and most reports which do not mention seizures are of patients who died before 2 months. Severe psychomotor retardation is constant and spastic hypertonicity progressively replaces the hypotonia. All diets have failed to modify the course of the disease, even if they are successful in lowering the blood glycine level (Koepp et al. 1973 Mises et al. (1978). In all cases, the EEG is severely abnormal. In 23 of 31 cases in which records were obtained during the first two weeks of life the description is suggestive of a periodical pattern (Bachmann et al. 1971, Krieger and Hart 1974, Piussan et al. 1975 12 cases, 1978). In 13 of these 23 patients, the EEG course could not be followed, because of an early death (Piussan et al. 1975, Bachmann et al. 1971, von Schreier and Muller 1964, Shuman et al. 1978, Mises et al., 9 cases, 1978. In the remaining 10 patients and in the 8 infants first studied after age 2 weeks (Baumgartner et al. 1969, Ferdinand et al. 1970, De Groot et al. 1975, Koepp et al. 1973, Morel 1976, Rampini et al. 1967, Reploh et al. 1973, Ziter et al. 1968), the EEG displayed more or less typical hypsarrhythmic features, starting from an average of 3 months. As to the clinical EEG correlations, the myoclonias were already evident at a time when the EEG was of periodical paroxysmal type in all 31 cases. When the h~~s a r r h y t h m i c pattern appeared, seizures of various types, including infantile spasms and partial and/or generalized motor fits, were already present. No effect of any therapy was observed with various treatments, including corticotropin, neither on the seizures nor on the EEG abnormalities. All cases in which typical EEG anomalies were recorded had a high CSF glycine level when this was measured (24 of 31).
Thus, the data from the literature as well as those from our own cases confirm the existence of a very suggestive EEG picture with early abnormalities and a stereotyped course.
Neuropathological data A small number of pathological records on nonketotic h~perglycinemia have been published (Anderson 1969, Dietzel and Martin 1966, Rushton 1968, Shuman et al. 1978). The lesions have been found exclusively in the white matter of the brain. They consist of a spongiosis which is limited to the areas already myelinated. Our findings were entirely consistent with those described in babies who died during the first days of life (Anderson 1969, Dietzel and Martin 1966, Rushton 1968). At this stage, the disorder does not affect the grade of myelination, which is normal for the age. In patients surviving to 24 and 36 months, Shuman et al. (1978) noted a poor myelination, without myelin breakdown products, in addition to the spongy state. According to these workers, the importance of the spongiosis is related to the degree of myelination of the structures and,to the rapidity of the myelination process. Thus, the faster the myelination in a given tract, the greater the vacuolation. The spongiosis has an intram~elinic location and is comparable to the vacuolation described in triethyltin intoxication (TO-rack et al. 1970) and in hexachlorophene intoxication (GoutiJres and Aicardi 1977, Shuman et al. 1970). The marked degree of spongiosis we observed in the subependymal area, along the third ventricle and in the molecular layer of the cortex may be consistent with a local toxic effect from the high glycine concentration in the CSF. Glycine in CSF, however, cannot be the only factor since in one case of hyperglycinemia without excess glycine in the CSF (case 3 of Shuman et al. 1978), a similar neur~patholo~ical aspect was observed.

Discussion
The individuality of non-ketotic hyperglycinemia was first established by the association of a severe neonatal neurological disorder with a high plasma glycine level wi,thout metabolic acidosis (Ferdinand et al. 1970, Leupold et al. 1974, Mabry and Karam 1963, Rampini et al. 1967, Rees et al. 1972, von Schreier and Miiller 1964, Simila and Visakorpi 1970, Ziter et al. 1968). An additional criterion was the absence of metabolic disturbance on the pathways of the branched chain amino acids, which was shown to be characteristic of the ketotic hyperglycinemias (Bachmann et al. 1971, Baumgartner et al. 1969, Corbeel et al. 1975, de Groot et al. 1970, Koepp et al. 1973, Krieger and Hart 1974, Molina-Andreu and Gonzales-Jorge 1975, Okken et al. 1971, Piussan et al. 1975, Saudubray et al. 1974). It was found subsequently that a specific defect of the glycine-cleavage enzymatic system was responsible for the high blood glycine level, as shown by the lack of conversion of the carbon 2 of glycine, to carbon 3 of serine (Ando et al. 1968, Gerritsen et al. 1965, Reploh et al. 1973, Sass-Kortsack et al. 1965, Trijbels et al. 1974. A high level of glycine in the CSF was demonstrated in patients with nonketotic hyperglycinemia (Bachmann et al. 1971, Baumgartner et al. 1969, Rampini et al. 1967, Seppalainen and Simila 1971, Ziter et al. 1968, Applegarth and Poon 1975. In 1972, Levy et al. (1972) demonstrated that CSF glycine was elevated in cases of nonketotic hyperglycinemia, while it was normal in infants with hyperglycinemia. Perry et al. (1975) documented a high level of glycine in brain tissue of patients with nonketotic hyperglycinemia with elevated CSF glycine, especially in the cerebellar cortex, putamen, pallidum and spinal cord. Contrarywise, brain glycine was not elevated in patients with hyperglycinemia without ketosis who did not display the characteristic symptoms and signs of nervous system involvement (cases 1 and 2 of Perry et al. 1975). Moreover, these workers found a high brain level of glycine in a patient with typical neurological features although without hyperglycinemia. These findings are in agreement with those of Morel (1976) who also found high brain glycine levels in symptomatic patients, and those of Bank and Harrow (1972) who found no sign of nervous involvement in 3 patients without hyperglycinorrhachia but with hyperglycinemia.
Therefore, the origin of the neurological picture of nonketotic hyperglycinemia is clearly related to elevated CSF glycine rather than to hyperglycinemia per se. The only known exception is represented by the two atypical cases of Holmgren and Son Blomquist (1977), in whom both nonketotic hyperglycinemia and an elevated CSF level of glycine were present without severe mental retardation or seizures. We suggest therefore that the term gljrcine encephalopathy be substituted to nonketotic hyperglycinemia, since the characteristic clinical and EEG picture is not dependent on the blood level of glycine. Perry et al. (1975), Morel (1976) and one of us (Dalla Bernardina et al. 1977) have already proposed this name for the specific encephalopathy with epilepsy described in this work. Table I shows the proposed classification of the hyperglycinemias in which the term nonketotic hyperglycinemia is applied only to those cases of hyperglycinemia without ketosis and without hyperglycinorrhachia (Table I).
Glycine encephalopathy, on the other hand, would be characterized by: a) early appearance in a newborn, after a symptomfree interval of 18-72 hours, of lethargy, hypotonia, segmental myoclonias and respiratory disturbances without metabolic acidosis; b) EEG abnormalities present from the onset of clinical disturbances, consisting of paroxysmal bursts of atypical spike-waves occurring periodically on a very de-  (Morel 1976), always featuring hyperglycinorrhachia and most often hyperglycinemia.
The early recognition of this encephalopathy is of great clinical importance, since respiratory support, which is often necessary duri,ng the neonatal period, does not seem warranted in view of the uniformly poor neurological outcome, and since genetic counselling should be offered.