What are the neurological symptoms and signs of schizophrenia?

Neurological Symptoms and Signs of Schizophrenia

Schizophrenia presents with distinct neurological symptoms and signs that can be categorized into positive symptoms, negative symptoms, and cognitive impairments, with cognitive deficits representing the core dysfunction of the disorder. 1

Symptom Categories

Positive Symptoms

Positive symptoms represent an excess or distortion of normal functions:

• Hallucinations - predominantly auditory, but can include visual, tactile, olfactory, or gustatory 2
• Delusions - fixed false beliefs not amenable to change despite contradictory evidence 2
• Thought disorder - disorganized thinking manifested through:
  • Loose associations
  • Illogical thinking
  • Impaired discourse skills 2
• Disorganized behavior - bizarre actions, inappropriate social behavior 2

Negative Symptoms

Negative symptoms represent diminished or absent normal functions, organized into two clusters:

• Diminished expression:

  • Flat affect
  • Reduced emotional expressivity
  • Poverty of speech 3

• Avolition:

  • Anhedonia (inability to experience pleasure)
  • Reduced motivation
  • Social withdrawal
  • Apathy 3, 4

Cognitive Impairments

Cognitive deficits are now recognized as the core feature of schizophrenia 1:

• Working memory deficits - difficulty maintaining and manipulating information 1
• Attention deficits - problems with sustained and selective attention 1
• Executive function impairments - difficulties with planning, problem-solving, and cognitive flexibility 3
• Information processing deficits - reduced speed and efficiency of mental operations 3
• Verbal memory impairments - problems with encoding and retrieving verbal information 3

Neurobiological Manifestations

Brain Structure Abnormalities

• Progressive increase in ventricular size during adolescence 2
• 4-fold greater decrease in cortical gray matter volume, particularly in frontal and temporal regions 2
• Smaller total cerebral volumes correlating with negative symptoms 2
• Frontal lobe dysfunction 2

Neurotransmitter Disturbances

• Dopamine dysregulation - excess in mesolimbic pathways, deficiency in mesocortical pathways 2
• Glutamate abnormalities - NMDA receptor dysfunction 2

Neurological Soft Signs

• Deficits in smooth-pursuit eye movements 2
• Abnormal autonomic responsivity 2
• Motor coordination problems 2

Cognitive-Symptom Relationships

• Paranoid vs. Non-paranoid subtypes:

  • Non-paranoid patients show reduced attention to contextual aspects of stimuli
  • Paranoid patients maintain better attention to connotative elements 5

• Positive-Negative symptom correlations:

  • Positive symptoms correlate with auditory-processing deficits
  • Negative symptoms correlate with visual/motor dysfunctions 5

• Specific symptom mechanisms:

  • Hallucinations associated with deficits in discriminating information sources
  • Delusions related to abnormal inference processes and perceptual experiences 5

Premorbid and Developmental Manifestations

• Social withdrawal and isolation

• Academic difficulties

• Speech and language problems

• Developmental delays

• Motor impairments 2

• IQ often in borderline to mentally retarded range (10-20% of cases) 2

• Language and communication deficits common 2

Clinical Implications

• Early identification of cognitive and negative symptoms is crucial as they strongly predict functional outcomes 3
• Cognitive deficits are enduring features not significantly improved by current antipsychotic medications 3
• Cognitive remediation therapy shows promise for improving cognitive impairments and social functioning 3

Common Pitfalls in Assessment

• Mistaking developmental language disorders for thought disorder 2
• Overlooking cognitive deficits which may be more predictive of functional outcomes than positive symptoms 1
• Failing to distinguish between primary negative symptoms and secondary negative symptoms (due to medication, depression, or social isolation) 3
• Not recognizing that cognitive impairments may be present even when positive symptoms are well-controlled 3

The neurological symptoms of schizophrenia reflect underlying brain dysfunction across multiple systems, with cognitive deficits representing the core feature that most significantly impacts long-term functioning and quality of life.