What part of the brain is most responsible for hemineglect?

The Right Hemisphere Parietal Lobe is Most Responsible for Hemineglect

The right inferior parietal lobule is the brain region most responsible for hemineglect, with damage to this area consistently producing the perceptive/visuo-spatial components of neglect syndrome. 1

Neuroanatomical Basis of Hemineglect

Hemineglect (also called unilateral neglect, spatial neglect, or hemispatial neglect) is a neuropsychological condition characterized by a deficit in attention to and awareness of one side of space, typically the left side following right hemisphere damage. The neuroanatomical correlates include:

Primary Regions:

• Right Inferior Parietal Lobule: Most strongly associated with the perceptive/visuo-spatial component of neglect 1
• Right Dorsolateral Prefrontal Cortex: Linked to the exploratory/visuo-motor component 1
• Deep Temporal Lobe Regions: Associated with allocentric/object-centered neglect 1

White Matter Connections:

• Damage to paraventricular white matter tracts often produces more severe neglect by disrupting connections between multiple functional domains 1

Clinical Manifestations

Hemineglect typically presents with:

• Lack of awareness of stimuli on the contralesional side (usually left side)
• Failure to dress, groom, or attend to the contralesional side of the body
• Inability to navigate properly in space
• Difficulty with reading (neglecting the left side of text)
• Problems with drawing (omitting details on the left side)
• Unawareness of the deficit (anosognosia) 2

Functional Components of Hemineglect

Research has identified three distinct components of hemineglect, each with specific neural correlates:

1. Perceptive/Visuo-spatial Component: Inability to perceive stimuli in the contralesional space

   • Neural correlate: Right inferior parietal lobule 1

2. Exploratory/Visuo-motor Component: Failure to explore the contralesional space

   • Neural correlate: Right dorsolateral prefrontal cortex 1

3. Allocentric/Object-centered Component: Neglect of the contralesional side of individual objects

   • Neural correlate: Deep temporal lobe regions 1

Diagnostic Considerations

Hemineglect is often associated with right hemisphere stroke, particularly affecting the right parietal cortex 2. It's important to distinguish hemineglect from:

• Visual field cuts (hemianopia)
• Primary sensory deficits
• Impaired attention
• Planning or visuospatial deficits 2

Rehabilitation Approaches

Treatment approaches for hemineglect can be categorized as:

1. Extrinsic ("Top-down") Approaches:

   • Visual scanning therapy - training patients to actively move gaze leftward 3
   • Strategy training 2
   • Task practice with mental rehearsal 2

2. Intrinsic ("Bottom-up") Approaches:

   • Vestibular stimulation
   • Sensory activation of the affected limb
   • Transcranial magnetic stimulation 3
   • Mirror therapy (recommended with "weak for" evidence) 2
   • Prism adaptation 2

3. Technology-Based Interventions:

   • Movement detection bracelets with visual-acoustic alarms (shown to improve neglect hand use in vision-dependent tasks) 4

Prognosis

Many patients with mild neglect show spontaneous improvement within weeks of onset, while those with profound neglect may improve over many months 2. The presence of hemineglect is a significant contributor to poor prognosis after stroke 2.

Clinical Pearls and Pitfalls

• Hemineglect is more common after right hemisphere than left hemisphere stroke 2
• Patients with hemineglect do not realize they are failing to attend to one side of their world, creating significant safety concerns 2
• The disorder is heterogeneous, with different patients showing different combinations of deficits 1
• Neglect can significantly impair rehabilitation outcomes and functional independence
• Assessment should include multiple tests as different tests may identify different aspects of neglect 2

Understanding the specific neural correlates of hemineglect components can help guide more targeted rehabilitation approaches for this challenging neurological condition.