Intrathecal-specific glutamic acid decarboxylase antibodies at low titers in autoimmune neurological disorders.

Autoantibodies to glutamic acid decarboxylase (Gad-Abs) are implicated in various neurological syndromes. The present study aims to identify intrathecal-specific GAD-Abs and to determine clinical manifestations and treatment outcomes. Nineteen patients had GAD-Abs in cerebrospinal fluid but not in paired serum samples. Neurological syndromes included limbic encephalitis, temporal lobe epilepsy, cerebellar ataxia, autonomic dysfunction, and stiff-person syndrome. Immunotherapy had beneficial effects in 57.1% of patients, and the patients with limbic encephalitis responded especially well to immunotherapy. Intrathecal-specific antibodies to GAD at low titers may appear as nonspecific markers of immune activation within the central nervous system rather than pathogenic antibodies causing neuronal dysfunction.

Qualitative and quantitative evidence of anti-glutamic acid decarboxylase-specific intrathecal antibody synthesis in patients with stiff person syndrome.

BACKGROUND: The stiff person syndrome (SPS) is a CNS disorder of putative autoimmune aetiology, which is clinically characterized by severe rigidity and spasms. In most cases, SPS is associated with serum antibodies against glutamic acid decarboxylase (GAD-Ab). Recent studies suggested that GAD-Ab might be directly involved in the pathogenesis of SPS. Further support for this hypothesis would come from studies providing qualitative evidence for the presence of GAD-Ab-producing B cell clones within the CNS of patients with SPS. OBJECTIVE AND METHODS: To address that issue, we (i) analysed paired cerebrospinal fluid (CSF) and serum samples from ten GAD-Ab positive patients with SPS and controls by an antigen-driven affinity blotting technique for the presence of GAD-specific oligoclonal IgG bands (OCBs) in the CSF, and (ii) examined the immunoreactive pattern of CSF and serum IgG to recombinant GAD by immunoblotting. To confirm our results quantitatively, we (iii) assessed anti-GAD antibody reactivity in CSF and serum using ELISA and evaluated the GAD-specific antibody index. RESULTS: GAD-specific oligoclonal bands exclusively or predominately in CSF compared to the corresponding serum were detected in 10/10 patients with GAD-positive SPS but in none of the controls. Immunoblotting revealed stronger staining in the CSF, suggestive of intrathecal IgG synthesis, in 7/10 patients upon visual inspection, and in 8/10 patients upon densitometric analysis. A positive GAD-specific antibody index was found in 9/10 patients. CONCLUSIONS: Here we demonstrate for the first time that IgG OCBs in SPS bind GAD. Our findings contribute to the ongoing discussion on whether the autoimmune process against GAD is involved in the pathogenesis of SPS by indicating that anti-GAD-Ab is produced by B cell clones within the CNS.

Tremor of the mouth floor and anti-glutamic acid decarboxylase autoantibodies.

Involuntary movements of the mouth can present as palatal tremor, which is frequently associated with hypertrophy of the inferior olivary nucleus and can be accompanied by contraction of other muscles of the head. We report the case of a 39-year-old man with autoimmune thyroiditis and diabetes who complained of involuntary rhythmic tremor involving the muscles of the floor of the mouth, which interfered with breathing and swallowing. Cerebrospinal fluid (CSF) examination showed the presence of oligoclonal bands and screening for anti-neuronal antibodies revealed high titres of anti-glutamic acid decarboxylase autoantibodies (GAD-Ab). Tremor responded to treatment with benzodiazepines. The correlation between the tremor and antibody positivity is unclear although an alteration of the gabaergic system mediated by the antibodies may be hypothesised on the basis of an inflammatory CSF profile.

The stiff-person syndrome. Case report.

The stiff-person syndrome is a rare and disabling disorder, characterized by muscle rigidity with superimposed painful spasms involving axial and limb musculature. The clinical symptoms are continuous contraction of agonist and antagonist muscles caused by involuntary motor-unit firing at rest and the spasms that are precipitated by tactile stimuli, passive strach, volitional movement of affected or unaffected muscles, startling noises and emotional stimuli. Both the rigidity and the spasms are relieved by sleep, general anaesthesia, myoneural blockade and peripheral nerve blockade. The cause of the stiff-person syndrome is unknown but an autoimmune pathogenesis is suspected because 1) the presence in the cerebrospinal fluid (CSF) of antibodies against glutamic acid decarboxylase (GAD), the rate-limiting enzyme for the synthesis of the inhibitory neurotrasmitter gamma-aminobutyric acid (GABA), 2) the association of the disease with other autoimmune disorders, 3) the presence of various autoantibodies and 4) a strong immunogenetic association. The stiff-person syndrome is clinically elusive but potentially treatable and should be considered in patients with unexplained stiffness and spasms. Drugs that enhance GABA neurotransmission, such as diazepam, vigabatrin and baclofen, provide modest relief of clinical symptoms. Immunomodulatory agents such as steroids, plasmapheresis and intravenous immunoglobulin, seem to offer substantial improvement.

Stiff person syndrome: quantification, specificity, and intrathecal synthesis of GAD65 antibodies.

OBJECTIVE: To characterize the specificity of anti-GAD(65) antibodies in patients with stiff person syndrome (SPS), quantify antibody titers, and examine antibody production within the CNS. METHODS: The authors studied 18 patients with SPS and positive serum immunoreactivity to gamma-aminobutyric acid (GABA)-ergic neurons. The reactivity of serum and CSF to purified GAD antigen was examined by Western blots, and the anti-GAD(65) antibody titers in serum and CSF were quantified by ELISA and compared with 70 disease controls (49 with other autoimmune disorders and 11 with insulin-dependent diabetes mellitus). The intrathecal synthesis of anti-GAD(65) IgG was calculated, and the functional significance of the antibodies was examined by measuring the GABA levels in the CSF. RESULTS: The serum and CSF of all selected patients with SPS had high anti-GAD(65) titers (from 7.0 to 215 microg/mL in serum and from 92 to 2500 ng/mL in CSF) and immunoreacted strongly with recombinant GAD(65) on Western blots and with GABA-ergic neurons on rat cerebellum. Among controls, only the serum of eight patients with insulin-dependent diabetes mellitus had low anti-GAD(65) antibody titers (from 200 to 1760 ng/mL) but no reactivity to recombinant GAD(65). The CSF showed oligoclonal IgG bands in 10 (67%) of 15 patients and an increased anti-GAD(65)-specific IgG index in 11 (85%) of 13. The mean level of GABA in the CSF was lower in patients with SPS than in controls. CONCLUSIONS: In patients with SPS, there is marked intrathecal antibody response against neuronal GAD(65) epitopes, indicating a clonal B cell activation in the CNS. Anti-GAD(65) antibodies at high titers, when confirmed with immunoblots, are highly specific for SPS and appear to impair GABA synthesis.

Cerebellar ataxia with anti-glutamic acid decarboxylase antibodies: study of 14 patients.

BACKGROUND: Antibodies to glutamic acid decarboxylase (GAD-Ab) are described in patients with insulin-dependent (type 1) diabetes mellitus (IDDM), in stiff-man syndrome, and, recently, in a few patients with cerebellar ataxia. OBJECTIVES: To show a link between GAD-Ab and some patients with cerebellar ataxia and to clarify their clinical and immunologic profiles. METHODS: Serum samples were selected from 9000 samples of 4 laboratories. The selection criterion was an immunohistochemical pattern compatible with GAD-Ab that was confirmed by radioimmunoassay. We identified 22 patients with stiff-man syndrome and 14 with cerebellar ataxia and GAD-Ab. RESULTS: Thirteen of the 14 patients with cerebellar ataxia and GAD-Ab were women, and 11 had late-onset IDDM. Patients did not have clinical or radiologic evidence of brainstem involvement. Ten patients had oligoclonal IgG bands in the cerebrospinal fluid, and intrathecal GAD-Ab synthesis was observed in 5 of the 6 patients studied. The level of GAD-Ab of these patients was similar to those with stiff-man syndrome and significantly higher than those with IDDM or with polyendocrine autoimmunity (P<.001). However, the GAD-Ab levels of 6 of the 9 patients with polyendocrine autoimmunity overlapped with those of patients with cerebellar ataxia. CONCLUSIONS: These results suggest a link between high level of GAD-Ab and some cases of cerebellar ataxia, particularly women with IDDM. If high serum levels of GAD-Ab are detected, the cerebrospinal fluid should be evaluated for the presence of oligoclonal IgG bands and intrathecal synthesis of GAD-Ab to further prove an autoimmune origin of the syndrome.

Severe insulin resistance in a patient with type 1 diabetes and stiff-man syndrome treated with insulin lispro.

We describe a patient with type 1 diabetes with recurrent diabetic ketoacidosis and severe insulin resistance. Extensive evaluation of the etiology of the insulin resistance did not reveal an etiology, and well over 1000 U of daily insulin did not prevent the ketoacidosis. Her blood glucose and insulin requirements were improved with glucocorticoids and octreotide, but the effects of both of these agents were short-lived. She was given a trial of insulin lispro with immediate and dramatic effects, lowering her HbA1c from 14.6 to 5.1% in 7 months with a decrease in insulin requirements of 1600-100 U per day. Besides her diabetes, she had a history of pain and stiffness affecting numerous muscle groups, and hospitalization was required for pain control. The diagnosis of stiff-man syndrome (SMS) was confirmed with high titers of glutamic acid decarboxylase 65 antibodies in both serum and cerebral spinal fluid. In summary, we describe the first patient with type 1 diabetes, SMS, and severe insulin resistance. Although the etiology of the insulin resistance is unknown, due to the efficacious response to insulin lispro, hydrocortisone, and perhaps octreotide, we propose an immune-mediated etiology. Although rare, this syndrome needs to be considered as an etiology of insulin resistance.

Inhibition of gamma-aminobutyric acid synthesis by glutamic acid decarboxylase autoantibodies in stiff-man syndrome.

Stiff-man syndrome (SMS) is a rare disorder of the central nervous system thought to result from an impairment of gamma-aminobutyric acid (GABA)ergic neurotransmission. Autoantibodies to the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD), present in about 60% of SMS patients, have suggested an autoimmune pathogenesis of SMS. By using serum or cerebrospinal fluid from 25 SMS patients, we assessed the effect of GAD autoantibodies (GAD-A) on GAD enzymatic activity in vitro; 83% of GAD-A-positive SMS sera reduced GABA production in crude rat cerebellar extracts, whereas GAD-A- sera from SMS patients or healthy blood donors did not alter the enzyme activity. Inhibition of GABA synthesis by SMS sera was dose dependent and mediated by the purified IgG fraction of the sera. Human monoclonal GAD65-A and IgG purified from serum of GAD-A-positive patients with insulin-dependent diabetes or autoimmune polyendocrine syndrome did not affect GAD activity, suggesting that a specific epitope recognition of GAD-A mediates inhibition of GAD. The disease-specific detection of GAD-inhibitory antibodies is compatible with their functional involvement in the etiopathology of SMS; the relevance of such antibodies in vivo, however, remains to be determined.

Levels of glutamic acid decarboxylase (GAD), gamma amino butyric acid transaminase (GABA-T), glutamic acid dehydrogenase (GLDH) and proteins in cerebrospinal fluid of certain neurological disorders.

Important glutamic acid metabolising enzymes in brain namely GAD, GABA-A and GLDH have been studied in the CSF of tuberculous meningitis (TBM), pyogenic meningitis (PM) and brain tumor (BT). The levels of GAD were reported as picomoles of GABA formed/mg of protein/hour. The control levels of the enzymes were GAD = 129 +/- 54, GABA-T = 533 +/- 146 and GLDH...O. 198 +/- 0.097. The levels of GAD were significantly increased (P < 0.001), in both TBM and PM, the values were 302 +/- 81 and, 290 +/- 97 respectively. The GABA-T levels were significantly raised (P < 0.001) only in PM cases 639 +/- 171. The values were reported as nano moles of GABA transformed/mg of protein/hour. The CSF-GLDH levels (unit/litre) showed significant elevation (P +/- 0.001) in TBM in PM, the values were 0.41 +/- 0.1 and 0.41 +/- 0.18 respectively. The CSF proteins were markedly elevated in all the conditions.

Senile dementia and presenile dementia.

Neurotransmitters including acetylcholine, dopamine, norepinephrine, serotonin, GABA and vasopressin were examined in control subjects and patients with Alzheimer-type dementia, involving presenile and senile dementia. Neurotransmitters exhibited various mode of changes with aging. Abnormalities found in senile or presenile dementia were not always parallel to the age-related changes. These results suggest that Alzheimer-type dementia cannot be understood as an accelerated senescence, but other etiological factors might be introduced for the manifestation of the dementia. Moreover, the disturbance in neurotransmitters revealed a difference between presenile Alzheimer's disease and senile dementia, indicating that further studies should be carried out taking the age of onset into consideration.

Glutamic acid decarboxylase in cerebrospinal fluid in infancy and childhood. Part I. Glutamic acid decarboxylase activity in cerebrospinal fluid of normal infants and children.

Glutamic acid decarboxylase (GAD) activity in the cerebrospinal fluid (CSF) of normal infants (n:14) and children (n:28) was determined by measuring the amount of 14CO2 released from L-[1-14C]-glutamic acid. The mean GAD activity in CSF of infants and children was 5.2 +/- 2.5 pmol CO2 formed/hr/ml. Dividing these subjects into 4 groups according to age, GAD activities in CSF were 5.4 +/- 1.6 pmol CO2 formed/hr/ml in neonates (0-1 m), 3.6 +/- 1.6 pmol CO2 formed/hr/ml in infants (2-12 m), 3.9 +/- 1.1 pmol CO2 formed/hr/ml in young children (2-6 yr) and 7.1 +/- 2.3 pmol CO2 formed/hr/ml in school children (7-16 yr), respectively. In neonates and school children, GAD activities were significantly higher (p less than 0.001) than those in the other age groups. In infants under 6 months of age, a significantly negative correlation between GAD activity in CSF and their ages was recognized (r = -0.52, p less than 0.001). In infants and children ranging from 6 months to 16 years of age, a significantly positive correlation between GAD activity in CSF and their ages was found (r = 0.67, p less than 0.001). These data suggest that high GAD activity in neonates may be due to hypoxia at birth and the activity gradually increases from 6 months to 15 years of age.

Glutamic acid decarboxylase in cerebrospinal fluid in infancy and childhood Part II. Glutamic acid decarboxylase activity in cerebrospinal fluid of children with neurological diseases.

Glutamic acid decarboxylase (GAD) activity in cerebrospinal fluid (CSF) was determined in 53 patients with neurological diseases as follows: Epilepsy (n:17), febrile convulsions (n:3), meningoencephalitis (n:17), encephalopathies (n:10), CNS leukemia (n:3), congenital hydrocephalus (n:2) and pseudoileus neonatorum (n:1). Compared with the mean normal value (5.2 +/- 2.5 pmol CO2 formed/hr/ml) reported in Part I, a significant increase of GAD activity in CSF was demonstrated in patients with uncontrolled epileptic seizures (11.4 +/- 3.9 pmol CO2 formed/hr/ml), febrile convulsions (13.5 +/- 8.7), viral meningitis with or without encephalitis (20.3 +/- 13.6), encephalopathies (30.0 +/- 25.9), CNS leukemia (11.1 +/- 5.0), congenital hydrocephalus (20.5 +/- 7.3) and pseudoileus neonatorum (28.6). Markedly high GAD activity was found in patients with CNS leukemia several days after intrathecal injection of methotrexate (39.8 +/- 18.0). On the other hand, significantly low GAD activity was shown in patients with bacterial meningitis or brain abscess (1.3 +/- 1.2). This suggests that some bacterial factors may be inhibitory toward GAD activity in CSF. High GAD activity in CSF may be useful as an indicator of aseptic brain dysfunction, although it was not always correlated with the severity of symptoms.