SENSORY LESIONSENSORY LESION

By Prof. ASHRAF HUSAINBy Prof. ASHRAF HUSAIN

Sensory Pathway Sensory Pathway LesionsLesions

A. Dorsal column syndrome A. Dorsal column syndrome

includes the fasciculi gracilis (T6–S5) and includes the fasciculi gracilis (T6–S5) and cuneatus (C2–T6) and the dorsal roots.cuneatus (C2–T6) and the dorsal roots.

is seen in subacute as tabes dorsalis is seen in subacute as tabes dorsalis combined degeneration (vitamin B12 combined degeneration (vitamin B12 neuropathy).neuropathy).

is seen in neurosyphilis as and in is seen in neurosyphilis as and in nonsyphilitic sensory neuropathies.nonsyphilitic sensory neuropathies.

A. Dorsal column syndrome (contd)A. Dorsal column syndrome (contd)

results in the following ipsilateral sensory deficits found results in the following ipsilateral sensory deficits found below the lesion:below the lesion:1)loss of tactile discrimination1)loss of tactile discrimination2)loss of position and vibratory sensation2)loss of position and vibratory sensation3)astereognosis3)astereognosis4) sensory loss4) sensory loss5)paraesthesia and pain (dorsal root irritation)5)paraesthesia and pain (dorsal root irritation)6) hyporeflexia (due todorsal root deafferentation)6) hyporeflexia (due todorsal root deafferentation)7) urinary incontinence, constipation and impotence (due 7) urinary incontinence, constipation and impotence (due todorsal root deafferentation)todorsal root deafferentation)8) romberg sign (sensory dystaxia) (standing patient is 8) romberg sign (sensory dystaxia) (standing patient is more unsteady with eyes closed)more unsteady with eyes closed)

B. Lateral spinothalamic tract lesion B. Lateral spinothalamic tract lesion

results in contralateral loss of pain and results in contralateral loss of pain and temperature sensation one segment below temperature sensation one segment below the level of the lesion.the level of the lesion.

C. Ventral spinothalamic tract C. Ventral spinothalamic tract lesion lesion

results in contralateral loss of light (crude) results in contralateral loss of light (crude) touch sensation three or four segments touch sensation three or four segments below the level of the lesion.below the level of the lesion.

does not appreciably reduce touch does not appreciably reduce touch sensation if the dorsal columns are intactsensation if the dorsal columns are intact

D. Dorsal spinocerebellar tract D. Dorsal spinocerebellar tract lesion lesion

results in ipsilateral leg dystaxia; patient results in ipsilateral leg dystaxia; patient has difficulty performing the heel-to-shin has difficulty performing the heel-to-shin test.test.

E. Ventral spinocerebellar tract E. Ventral spinocerebellar tract lesion lesion

results in contralateral leg dystaxia; patient results in contralateral leg dystaxia; patient has difficulty performing the heel-to-shin has difficulty performing the heel-to-shin test.test.

Peripheral Nervous System Peripheral Nervous System Lesions Lesions

may be sensory, motor, or combined.may be sensory, motor, or combined.

affect spinal roots, dorsal root ganglia, and affect spinal roots, dorsal root ganglia, and peripheral nervesperipheral nerves

A. Herpes zoster (shingles)A. Herpes zoster (shingles)

is a common viral infection of the nervous is a common viral infection of the nervous system.system.consists of an acute inflammatory reaction in the consists of an acute inflammatory reaction in the dorsal root or cranial nerve ganglia.dorsal root or cranial nerve ganglia.is usually limited to the territory of one is usually limited to the territory of one dermatome; the most common sites are T5 to dermatome; the most common sites are T5 to T10.T10.causes irritation of dorsal root ganglion cells, causes irritation of dorsal root ganglion cells, resulting in pain, itching, and burning sensations resulting in pain, itching, and burning sensations in the involved dermatomes.in the involved dermatomes.produces the characteristic vesicular eruption in produces the characteristic vesicular eruption in the affected dermatome.the affected dermatome.

B. Acute idiopathic polyneuritis B. Acute idiopathic polyneuritis (Guillain-Barré syndrome)(Guillain-Barré syndrome)

is also called postinfectious polyneuritis.is also called postinfectious polyneuritis.usually follows an infectious illness.usually follows an infectious illness.results from a cell-mediated immunologic results from a cell-mediated immunologic reaction directed at peripheral nerves.reaction directed at peripheral nerves.affects primarily motor fibers and causes affects primarily motor fibers and causes segmental demyelination and wallerian segmental demyelination and wallerian degeneration.degeneration.produces LMN(muscle weakness, flaccid produces LMN(muscle weakness, flaccid paralysis, and areflexia).paralysis, and areflexia).

B. Acute idiopathic polyneuritis B. Acute idiopathic polyneuritis (Guillain-Barré syndrome) contd.(Guillain-Barré syndrome) contd.

results in symmetric paralysis that begins results in symmetric paralysis that begins in the lower extremities and ascends to in the lower extremities and ascends to involve the trunk and upper extremities; involve the trunk and upper extremities; the facial nerve frequently is involved the facial nerve frequently is involved bilaterally.bilaterally.

elevates cerebrospinal fluid (CSF) protein; elevates cerebrospinal fluid (CSF) protein; however, the CSF cell count remains however, the CSF cell count remains normal.normal.

Figure 13.22 Sensory homunculus illustrating somatotopic organisation of the primary somatosensory cortex.

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© 2005 Elsevier

Parietal lobe lesions, Parietal lobe lesions, Left parietal Left parietal lobe lesions cause: lobe lesions cause:

partial seizures - paroxysmal attacks of partial seizures - paroxysmal attacks of abnormal sensations, spreading down the abnormal sensations, spreading down the contralateral side of the body (sensory seizures) contralateral side of the body (sensory seizures)

sensory/motor deficit - a contralateral sensory/motor deficit - a contralateral hemisensory loss and inferior visual field loss hemisensory loss and inferior visual field loss

Psychological deficit - an inability to name Psychological deficit - an inability to name objects (objects (anomiaanomia) and a loss of literacy, with ) and a loss of literacy, with inability to read (inability to read (alexiaalexia), to write (), to write (agraphiaagraphia) and ) and to calculate (to calculate (acalculiaacalculia). ).

Right parietal lobe lesions causeRight parietal lobe lesions cause

partial seizures - paroxysmal attacks of sensory partial seizures - paroxysmal attacks of sensory disturbance affecting the contralateral side of the disturbance affecting the contralateral side of the body (simple sensory seizures) body (simple sensory seizures)

sensory/motor deficit - contralateral hemisensory sensory/motor deficit - contralateral hemisensory loss and an inferior visual field loss loss and an inferior visual field loss

psychological deficit - an inability to copy and psychological deficit - an inability to copy and construct designs because of spatial construct designs because of spatial disorientation (disorientation (constructional apraxiaconstructional apraxia). ).