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German Journal of Psychiatry

ISSN 1433-1055

Neurological and cognitive deficits in schizophrenic patients

Ahmed Mubarak, Abdou El Dod, and El Sayed Gad


Department of Neuropsychiatry, Faculty of Medicine, Tanta University, Tanta, Egypt.

Corresponding author: Professor Ahmed Mubarak, MD, Department of Neuropsychiatry, Faculty of Medicine, Tanta University, Tanta, Egypt; e-mail: amobarak@future.com.eg


Abstract

Background: Thirty schizophrenic patients were diagnosed according to DSM-IV criteria, 15 with predominantly negative symptoms assessed by the Scales of Assessment of Negative Symptoms (SANS) and 15 with predominantly positive symptoms assessed by the Scales of Assessment of Positive Symptoms (SAPS), and compared to 15 healthy controls. Probands were subjected to clinical psychiatric and neurological evaluation, using the Neurological Evaluation Scale (NES), and cognitive evaluation, using the Mini-Mental State Examination (MMSE) and Wechsler Adult Intelligence Scale (WAIS).

Objective: the objective was to detect any neurological and cognitive deficits and their relation to the symptomatology.

Results: A significantly higher NES score was found in all patients compared with the control group and in the negative compared with the positive symptoms group. This not only applied to the total score of the test, but also to its three components (motor co-ordination, sensory integration and sequencing of complex motor acts), although the difference between the two patient groups was not significant. Regarding the intellectual and cognitive results, the patients had lower scores in the MMSE than the controls; this was more pronounced in the schizophrenic patients with negative symptoms than in those with positive symptoms. The relationship of the scores to individual symptoms was also studied.

Conclusion: This study demonstrates the significance of neurological and cognitive deficits through quantitative measures. The relationship of such deficits to various schizophrenic symptoms could stimulate research into the biological basis of the pathogenesis of schizophrenia (German J Psychiatry 1999;2:22-33)

Key words: cognitive, negative symptoms, positive symptoms, schizophrenic, neurological deficits.

INTRODUCTION

Since the original formulations of Kraepelin and Bleuler, schizophrenia has been viewed as a disorder whose pathophysiology would ultimately be found in the brain (Blanchard and Neal, 1994), however, this mysterious malady has not readily yielded its secrets to science. classification of schizophrenic patients into positive and negative may provide a meaningful subtyping scheme and these symptoms may constitute two clinical syndromes subserved by different pathological processes (Andreasen and Olsen, 1982).

There is extensive evidences suggesting abnormal structure and function of the brain in schizophrenia (Roberts, 1991). Studying the brain structure by methods including computerised tomography (Lewis 1990) and magnetic resonance imaging (Young et al. 1991; Breir et al. 1992) permit the study of brain anatomy and possible structural abnormalities. however, analysis of regional cerebral blood flow, single photon emission computed tomography (Ingvar and Franzen, 1971) and positron emission tomography permit the study of the brain at work through the measurement of metabolic activity and neurotransmitter systems (Andreasen, 1988).

Evaluating the neurological deficits in schizophrenic patients will provide real clinical proof of organic pathology; presence of any relation of these neurological or cognitive deficits with the schizophrenic symptoms will be of value in evaluating the nature of the organic pathogenesis of schizophrenic patients.

In this study, we evaluated the neurological and cognitive status in the two subgroups of schizophrenia and correlated these deficits with the scales of negative and positive symptoms. This may help in finding a neurophysiological explanation of schizophrenic symptoms.

 

 

METHODS

Patients

The present study was conducted in the Department of Neuropsychiatry, Tanta University Hospital. The subjects of this study included patients and a control group. Thirty patients met the DSM-IV criteria for schizophrenia (American Psychiatric Association, 1994). Their ages ranged between 18 and 45 years, and their mean age was 28.7 (SD 6.99), twenty-five (83.3%) were males and 5 (16.7%) were females. They were divided into two groups according to Andreasen’s criteria of positive and negative schizophrenia. Group 1, schizophrenic patients with predominantly positive symptoms: Fifteen schizophrenic subjects, their ages ranged between 18 and 45 years, with a mean age of 27.8 (SD 7) years, 12 subjects (80%) were males and 3 (20%) were females. They fulfilled the following criteria: (1) At least one of the following is a prominent part of the illness (i.e. the global rating of this symptom was 4 or more): Severe hallucinations that dominate the clinical picture (auditory, haptic, or olfactory), severe delusions (may be persecutory, jealous, somatic. religious, grandiose, or fantastic), marked positive formal thought disorder (manifested by marked incoherence, derailment, tangentiality or illogicality), repeated instances of bizarre or disorganised behaviour; (2) none of the following is present to a marked degree (their global ratings were less than 4): alogia, affective flattening, avolition-apathy, anhedonia-asociality, attentional impairment. Group 2, schizophrenic patients with predominantly negative symptoms: Fifteen schizophrenic subjects, their ages ranged between 21 and 40 years, with a mean age of 29 (SD 5.85) years, 13 subjects (86.7%) were males and 2 (13.3%) were females. They had the following criteria: (1) at least two of the following are present to a marked degree (their global rating was 4 or more): alogia (e.g. marked poverty of speech, poverty of content of speech), affective flattening, anhedonia-asociality (e.g. inability to experience pleasure or to feel intimacy, few social contacts), avolition-apathy (e.g. anergia, impersistence at work or school), attentional impairment; (2) none of the following dominates the clinical picture or is present to a marked degree (their global rating was less than 4): hallucinations, delusions, positive formal thought disorder, bizarre behaviour. exclusion criteria were (1) any other psychiatric disorders other than schizophrenia (e.g. MR, other developmental disorders); (2) any coexisting neurological disorders (e.g. epilepsy, stroke etc.), (3) any family history of neurological disorders (e.g. epilepsy, ataxia etc.), (4) treatment with ECT within the past 6 months.

Assessment

patients were subjected to the following: (1) clinical psychiatric examination, (2) assessment of positive symptoms by the Scale for the Assessment of Positive symptoms (SAPS) and negative symptoms by the Scale for the Assessment of Negative symptoms (SANS) (Andreasen, 1984), (3) Clinical neurological examination, (4) evaluation of the neurological signs using the Neurological Evaluation Scale (NES) [Buchanan & Heinrichs, 1989], (5) Evaluation of cognitive function using the Mini-Mental State Examination (MMSE) [Folestein et al. 1975]; intelligence was assessed using the Wechsler Adult Intelligence Scale (WAIS); verbal IQ, performance IQ and full scale IQ. The control group consisted of fifteen normal healthy subjects, their age and sex were matched with the patients' age and sex. They fulfilled the following criteria: (1) No history of psychiatric disorders, (2) No history of neurological disorders, (3) No family history of psychiatric or neurological disorders, (4) No history of medical illness, e.g. renal failure, chronic obstructive pulmonary disease (COPD). The control persons were subjected to neuropsychiatric evaluation, cognitive and intellectual evaluation using the MMSE and WAIS, and neurological evaluation using the NES.

Statistical analyses

The scores of the neurological evaluation scale in schizophrenic patients and control subjects were compared by means of the Wilcoxon-Mann-Whitney Test and two-tailed t-tests.

 

 

RESULTS

The results of the Scales of Assessment of Negative and Positive symptoms are presented in Table (1). A Mann-Whitney-Wilcoxon Rank Sum Test was calculated to compare the scores of the two scales in both groups of patients.

Table 1. Comparison of scores of SANS & SAPS in the 2 patient groups; Mann-Whitney-Wilcoxon Rank Sum Test

Scale

Subitem

Mean rank

Mann-Whitney

Wilcoxon Rank Sum

Z

2-tailed p

   

Negative symptoms schizophrenia

Positive symptoms schizophrenia

       

SANS

Alogia

22.63

8.37

5.5

339.5

4.4491

.0000

 

Affective blunting

22.33

8.67

10.0

335.0

-4.2835

.0000

 

Avolition

21.70

9.30

19.5

325.5

-3.9002

.0001

 

Anhedonia

21.80

9.20

18.0

327.0

-3.9448

.0001

 

Attentional disturbance

22.0

8.00

13

332.0

-4.1577

000

SAPS

Hallucinations

.00

8.00

       
 

Delusions

.00

8.00

       
 

Bizarre behaviour

11.67

19.33

55.0

175.0

-2.4133

.0158

 

Positive Formal thought disorders

5.17

10.37

9.5

15.5

-1.5449

.1224

 

Inappropriate affect

17.00

8.00

.0

51.0

-2.9653

.0030

The total score and the scores of each component of the test were significantly lower in schizophrenics than in controls (Table 2). Comparing the negative-symptom with the positive-symptom schizophrenics showed that negative-symptom patients have higher scores than the positive-symptom patients. However, the difference was significant only with regard to the total score and the score for sensory integration (Table 3).

Table 2. Comparison of the Neurological Evaluation Scale (NES) between all schizophrenic patients and control subjects; Mann-Whitney-Wilcoxon Rank Sum Test

Neurological evaluation scale(NES) Mean rank Mann-Whitney Wilcoxon Rank Sum Z 2-tailed p
  Schizophrenic patients (n=30) Control subjects

(n=15)

       
Total score 29.85 9.30 19.50 139.50 -4.96 0000
Motor co-ordination score 26.48 16.03 120.50 240.55 -2.71 0.017
Sensory integration score 28.42 12.17 62.50 182.50 -3.95 0.000
Sequencing of complex acts score 27.90 13.20 78.90 198.00 -3.61 0.000

 

Table 3. Comparison of the Neurological Evaluation Scale (NES) between negative- and positive-symptom schizophrenic patients using the Mann-Whitney-Wilcoxon Rank Sum Test

Neurological evaluation scale Mean rank Mann-Whitney Wilcoxon Rank Sum Z 2-tailed p
  Negative symptoms patients(n=15) Positive symptoms patients(n=15)        
Total score 19.10 11.90 58.50 286.50 -2.25 0.03
Motor co-ordination score 16.43 14.57 98.50 246.50 -0.67 0.54
Sensory integration score 20.20 10.80 42.00 303.00 -2.95 0.003
Sequencing of Complex acts score 15.70 15.30 109.50 235.50 -0.13 0.90

 

To analyse the results of cognitive evaluation, a two tailed t test for independent samples was calculated to compare the mean score of both the Mini-Mental State Examination (MMSE) and the Wechsler Adult Intelligence Scale (WAIS) tests. Comparing the mean score of all the patients with control subjects showed significantly lower MMSE scores in patients than in controls. The same results were obtained for the total, performance and verbal IQ of WAIS (Table 4). Comparing the mean score of negative- with positive-symptom schizophrenic patients showed highly significantly lower scores achieved by negative-symptom schizophrenics in all of the tests (Table 5).

Table 4. Results of the mini-mental state examination and Wechsler adult intelligence scale in all schizophrenic patients and control subjects

Test Schizophrenic patients (n=30) Control subjects

(n=15)

2-tailed t Df p
  Mean SD Mean SD      
Mini-mental state examination (MMSE) score 27.10 3.00 29.73 0.46 3.36 43 0.002
Wechsler adult intelligence scale (WAIS) Total IQ 94.47 3.25 100.60 1.99 6.67 43 0.000
  Performance IQ 95.57 3.28 100.60 3.23 4.88 43 0.000
  Verbal IQ 91.93 3.96 98.93 3.41 5.43 43 0.000

 

Table 5. Comparison between negative- and positive-symptom schizophrenic patients as regards the results of the mini-mental state examination and Wechsler adult intelligence scale

Test Negative-symptom patients (n=10) Positive-symptom patients (n=15) 2-tailed t Df p
  Mean SD Mean SD      
Mini-mental state examination (MMSE) score 25.33 3.33 28.87 0.92 3.96 28 0.000
Wechsler adult intelligence scale (WAIS) Total IQ 92.47 2.56 96.47 2.69 4.23 28 0.000
  Performance IQ 93.47 2.85 97.67 2.16 4.55 28 0.000
  Verbal IQ 89.53 2.97 94.33 3.35 4.15 28 0.000

Spearman’s correlation coefficient r was calculated to find out whether there is a correlation between neurological and cognitive functions and the scores of positive and negative symptom scales of schizophrenic patients (Table 6). The total neurological evaluation scale was positively correlated with the scores of alogia, affective blunting and disturbed attention. Sensory integration scores was positively correlated with the scores of alogia, affective blunting and disturbed attention, while the sequencing of complex acts was correlated with disturbed attention. There was no significant correlation between motor co-ordination scores and SANS. Correlating the scores of SAPS with neurological deficits showed a significant negative correlation of the bizarre behaviour and sensory integration scores.

The MMSE showed a significant negative correlation with all SANS subitems. The IQ showed a significant negative correlation with all items of SANS and a positive one with the formal thought disorder subitem of SAPS.

Table 6. Spearman’s correlation coefficient (r) between neurological and cognitive functions of schizophrenic patients and the score of positive and negative symptom scales

    Neurological Evaluation Scale   Cognitive Evaluation
      MMSE IQ
  Items of SAPS & SANS Total NES Motor
co-ordination
Sensory integration Sequencing of Complex acts   Total IQ

Score

Verbal IQ score Performance IQ Score
  Alogia .50** .26 .51** .156 -.70** -.58** -.56** -.65**
  Anhedonia .19 -.04 .32 -.16 -.50** -.45* -.39* -.49**
SANS Affective Blunting .64** .19 .77** .23 -.47** -.45* -.42* -.47**
  Disturbed Attention .61** .06 .65** .37* -.51** -.54** -.51** -.56**
  Avolition .14 -.01 .29 -.23 -.50** -.54** -.44* -.54**
  Delusions .39 -.13 .39 .20 .24 -.45* -.48 -.31
  Hallucinations .13 -.01 -.07 .30 -.17 -.25 -.22 -.32
  Bizarre Behaviour -.25 -.19 -.57** .01 .09 .12 .11 .22
SAPS Formal thought disorder -.45 .04 -.40 -.37 .24 .65** .61** .63**
  Inappropriate Affect .18 -.47 .34 -.18 -.18 -.40 -.42 -.43

* P<0.05 ** p<0.01

 

 

DISCUSSION

The results of this study are consistent with those of previous studies which demonstrated a higher prevalence of neurological signs in schizophrenics than in non-psychiatric control subjects (Moonstruck et al. 1982; Walker and Green, 1982; Woods et al. 1986, Heinrichs and Buchanan, 1988).

The presence of significant neurological signs in schizophrenic patients compared with controls confirms the notion that organicity is a part of the pathogenesis of schizophrenia and that it is only the nature and role of such organicity that remains open to debate. In this respect, the NES evaluates three important neurological areas: visual motor co-ordination, sensory integration and sequencing of complex acts. Although these areas were not significantly different among the two groups (negative- and positive-symptom schizophrenics), the study proved a significant correlation between the subitems of the NES and the SANS & SAPS as follows: sensory integration is correlated with both alogia and affective flattening, which is consistent with the studies of Rochford et al. (1970); Moonstruck et al. (1982). They found neurological impairment to be more common in negative schizophrenics, especially with withdrawal and affective flattening. Buchanan et al. (1990) found deficit schizophrenia to be associated with a high NES total score and the sensory integration subscore.

These findings lead us to postulate that these negative symptoms may be due to a disturbed integration of sensory input. the negative correlation of the sensory integration score with bizarre behaviour raises the question of whether this bizarreness is due to "over integration" of the sensory stimuli to the extent of "crawedness". These explanations open the way to further studies on the pathophysiological basis of psychiatric symptoms.

The negative correlation of the MMSE with the SANS score confirms previous reports. Seikan et al. (1994) found that schizophrenic patients had significantly lower mini-mental state examination (MMSE) scores than controls; Andreasen and Olsen (1982) found this to be correlated to negative symptoms. The association between schizophrenia and intellectual and cognitive impairments could be explained by: lower pre-morbid IQ, the chronicity of schizophrenic illness, or the cumulative (additive) effect of low pre-morbid IQ and the schizophrenic illness (Aylward et al. 1984; Crawford et al. 1992).

These studies demonstrated the significant burden of the disease process, particularly that of negative-symptom schizophrenia, on cognition, which may "in part " have an organic basis and may not be the case in positive-symptom schizophrenia.

McGlashan and Fenton, (1992) in a review on positive and negative schizophrenia concluded that lower IQ was associated with negative symptoms. Wagman et al. (1990) also found that patients with deficit symptoms scored lower in IQ tests. Our study confirmed these results. An interesting observation in negative schizophrenics was that positive formal thought disorders are correlated with higher IQ, which may indicate that this type of thought disturbance occurs mainly in the "intelligent mind".

In conclusion, neurological and cognitive deficits in schizophrenia are now a truism. Finding significant correlation with various schizophrenic symptoms will improve the knowledge of the pathogenesis of such symptoms. Our study has demonstrated some of these correlations and calls for confirmation or criticism by future studies.

 

 

REFERENCES

  1. American Psychiatric Association (1994): Diagnostic and Statistical Manual of Mental Disorders, 4th ed, (DSM-IV). Washington, DC.
  2. Andreasen NC (1984): Scale for thr assessment of positive symptoms (SAPS). The University of Iowa; Iowa City, Iowa
  3. Andreasen NC (1984): Scale for the assessment of negative symptoms (SANS). The University of Iowa; Iowa City, Iowa
  4. Andreasen NC (1988): Brain imaging: applications in psychiatry. Science, (239):13811388.
  5. Andreasen NC and Olsen S (1982): Negative versus positive schizophrenia: Definition and validation. Archives of General Psychiatry, (39): 789-794.
  6. Aylward E, Walker E, Bettes B (1984): Intelligence in schizophrenia: Meta - analysis of the research. Schizophrenia Bulletin, (100): 430 - 459.
  7. Blanchard JJ and Neal JM (1994): The neuropsychological signature of schizophrenia: generalized or differential deficit? American Journal of Psychiatry, (151): 40-48.
  8. Breier A, Buchanan RW, EI Kashe A, Munson RC, Kirkpatric KB, Gellad F(1992): Brain morphology and schizophrenia: a magnetic resonance imaging study of limbic, prefrontal cortex, and caudate structures. Archives of General Psychiatry, (49): 921-926.
  9. Buchanan RW, KirKpatrick B, and Heinrichs DW, Carpenter WT (1990): clinical correlates of the deficit syndrome of schizophrenia. American Journal of psychiatry, (147): 290 - 294.
  10. Buchanan RW, Heinrichs DW (1989): The neurological evaluation scale (NES): A structured instrument for the assessment of neurological signs in schizophrenia. Psychiatry Research, (27):335-350.
  11. Crawford JR, Besson JAO, Bremner M, Ebmeier KP, cochrane HB, and KirKwood K (1992): Estimation of premorbid intelligence in schizophrenia. American Journal of psychiatry (161): 69 - 74.
  12. Folstein MF, Folstein SE, McHugh PR (1975): Mini-mental state: A practical method for grading the cognitive state of patients for the clinician. Psychiatry Research, (12): 189.
  13. Heinrichs DW, Buchanan RW (1988): The significance and meaning of neurological signs in schizophrenia. American journal of psychiatry, (145): 11-18.
  14. Ingvar DH, Franzen G (1971): Abnormalities of cerebral blood flow distribution in patients with chronic schizophrenia. Acta Psychiatrica Scandinavica, (50): 425-62.
  15. Lewis S (1990): Computerized tomography in schizophrenia 15 years on. British Journal of Psychiatry, (157):16-24.
  16. Mcglashan TH, Fenton WS (1992): The positive - negative distinction in schizophrenia. Review of natural history validators. Archives of General psychiatry, (49): 63 - 72.
  17. Moonstruck Tc, Maher BA, Rucklos ME, Vereen DR (1982): Disturbed voluntary motor activity in schizophrenic disorder-psychological Medicine,(12): 73 - 84.
  18. Roberts GW (1991): Schizophrenia: A neuropathological perspective. British Journal of Psychiatry (158): 8-17.
  19. Rochford MD, Detre MD, and TUKER GJ (1970): Neuropsychological impairments in functional psychiatric diseases. Archives of General psychiatry, (22): 114-119.
  20. Saykin AJ, Shtasel DL, Gur RE, Kester DB, Mozley LM, Stafiniak P, Gur RC (1994): Neuropsychological deficits in neuroleptic naive patients with first episode schizophrenia . Archives of General Psychiatry (51):124-131.
  21. Wagman Rl, Gur Re, Mozley LH (1990): neuropsychological function in schizophrenia: selective impairment in memory and learning. schizophrenia Research, (12): 447 - 459.
  22. Walker E, Green M (1982): soft signs of neurological dysfunction in schizophrenia: An investigation of lateral performance. Biological psychiatry, (17): 381 - 386.
  23. Woods BT, Kinney DK, Yurgelun - Todd D (1986): Neurological abnormalities in schizophrenic patients and their families, 1: comparison of schizophrenic, bipolar, substance - abuse patients and normal control Archives of General psychiatry, (43): 657-663.
  24. Young AH, BlackHood DHR, Roxborough H, Mica I n JK, Kean D (1991J: A magnetic resonance imaging study of schizophrenia: brain structure and clinical symptoms. British Journal of Psychiatry, (158):158-164.