Focal neurologic signs

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Focal neurologic signs also known as focal signs or focal CNS signs are perceptual or behavioral impairments which are caused by lesions in a particular area of the central nervous system.

These signs are interpreted by neurologists to mean that a given disease process is focal rather than diffuse. (Focal disease processes include for example tumors or infarctions; diffuse disease processes include meningitis or encephalitis.)

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[edit] Frontal lobe signs

Frontal lobe signs usually involve the motor system, and may include many special types of deficit, depending on which part of the frontal lobe is affected:

  • unsteadiness in walking
  • muscular rigidity, resistance to passive movements of the limbs (hypertonia)
  • paralysis of a limb (monoparesis) or a larger area on one side of the body (hemiparesis)
  • paralysis head and eye movements
  • inability to express oneself linguistically, described as an expressive aphasia (Broca's aphasia)
  • focal seizures which can spread to adjacent areas (Jacksonian seizure)
  • grand mal or tonic-clonic seizures
  • changes in personality such as disinhibition, inappropriate jocularity, rage without provocation; or loss of initiative and concern, apathy, akinetic mutism, general retardation
  • "frontal release" signs, i.e. reappearance of primitive reflexes such as the snout reflex, the grasp reflex, and the palmar-mental reflex
  • unilateral loss of smell (anosmia)

[edit] Parietal lobe signs

Parietal lobe signs usually involve somatic sensation, and may include:

  • impairment of tactile sensation
  • impairment of proprioception, i.e. postural sensation and sensation of passive movement
  • sensory and visual neglect syndromes, i.e. inability to pay attention to things in certain parts of the person's sensory or spatial environment. This can be as extreme as denial of a limb.
  • loss of ability to read, write or calculate (dyslexia, dysgraphia, dyscalculia)
  • loss of ability to find a defined place (geographical agnosia)
  • loss of ability to identify objects based on touch (astereognosia)

[edit] Temporal lobe signs

Temporal lobe signs usually involve auditory sensation and memory, and may include:

  • deafness without damage to the structures of the ear, described as cortical deafness
  • tinnitus, auditory hallucinations
  • loss of ability to comprehend music or language, described as a sensory aphasia (Wernicke's aphasia)
  • amnesia, memory loss (affecting either long- or short-term memory or both)
  • other memory disturbances such as deja vu
  • complex, multimodal hallucinations
  • complex partial seizures (temporal lobe epilepsy)

[edit] Occipital lobe signs

Occipital lobe signs usually involve visual sensation, and may include:

  • total loss of vision (cortical blindness)
  • loss of vision with denial of the loss (Anton's syndrome)
  • loss of vision on one side of the visual field of both eyes (homonymous hemianopsia)
  • visual agnosias, i.e. inability to recognize familiar objects, colors, or faces
  • visual illusions such as micropsia (objects appear smaller) and macropsia (objects appear larger)
  • visual hallucinations, displaying elementary forms, such as zig-zags and flashes, in one half of the visual field only for each eye. (In contrast, temporal lobe visual hallucinations display complex forms, and fill the entire visual field.)

[edit] Cerebellar signs

Cerebellar signs usually involve balance and coordination, and may include:

  • unsteady and clumsy motion of the limbs or torso (ataxia)
  • inability to stand with eyes closed (positive Romberg sign)
  • inability to coordinate fine motor activities (intention tremor), e.g. "past-pointing" (pointing beyond the finger in the finger-nose test)
  • inability to perform rapid alternating movements (dysdiadochokinesis), e.g. inability to rapidly flip the hands
  • involuntary left-right eye movements (nystagmus)

[edit] Brainstem signs

Brainstem signs can involve a host of specific sensory and motor abnormalities, depending on which fiber tracts and cranial nerve nuclei are affected.

[edit] Spinal cord signs

Spinal cord signs generally involve unilateral paralysis with contralateral loss of pain sensation