Focal neurologic signs also known as focal neurological deficits or focal CNS
signs are impairments of nerve, spinal cord, or brain function that affects a
specific region of the body, e.g. weakness in the left arm, the right leg,
paresis, or plegia. Focal neurological deficits may be
caused by a variety of medical conditions such as head trauma, tumors
or stroke; or by various diseases such as meningitis or encephalitis or as a
side effect of certain medications such as those used in anesthesia.
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:
unsteady gait muscular rigidity, resistance to passive
movements of the limbs paralysis of a limb or a larger area on
one side of the body paralysis head and eye movements
inability to express oneself linguistically, described as an
expressive aphasia focal seizures which can spread to
adjacent areas 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
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
loss of ability to find a defined place loss of ability to identify objects
based on touch 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 amnesia, memory loss
other memory disturbances such as déjà vu
complex, multimodal hallucinations complex partial seizures
Occipital lobe signs Occipital lobe signs usually involve
visual sensation, and may include: total loss of vision
loss of vision with denial of the loss loss of vision on one side of the visual
field of both eyes visual agnosias, i.e. inability to
recognize familiar objects, colors, or faces
visual illusions such as micropsia and macropsia
visual hallucinations, displaying elementary forms, such as zig-zags and
flashes, in one half of the visual field only for each eye.
Limbic Signs Damage to the Limbic System involves
loss or damage to memory, and may include:
Loss or confusion of long-term memory prior to focal neuropathy
Inability to form new memories Loss of, or reduced emotions.
Loss of olfactory functions. Loss of decision making ability.
Cerebellar signs Cerebellar signs usually involve balance
and coordination, and may include: an ataxic gait with a broad base; the
patient falters to the side of the lesion.
inability to coordinate fine motor activities, e.g. "past-pointing"
inability to perform rapid alternating movements, e.g. inability to rapidly
flip the hands involuntary horizontal eye movements
dysarthria, usually with bilateral lesions. The speech has a halting
jerking quality 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. Spinal cord signs
Spinal cord signs generally involve unilateral paralysis with contralateral
loss of pain sensation References
Essentials of Kumar and Clark's Clinical Medicine, 5th Edition. Saunders
Elsevier, UK. 2012. page 725 See also
Focal and diffuse brain injury