USMLE Step 1 Neuroanatomy Review 27 14 Lesions of the Spinal Cord Part 2

USMLE Step 1 Neuroanatomy Review 27 14 Lesions of the Spinal Cord Part 2

 

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Play USMLE Audio MP3 27 14 Lesions of the Spinal Cord Part 2 Below

Begin 27 14 Lesions of the Spinal Cord Part 2 Transcription

Student doctor, please pause and list as many of the nine characteristics as you can of the dorsal column syndrome, or tabes dorsalis.

First, ipsilateral sensory deficits below the lesion.

Second, loss of tactile discrimination.

Third, loss of vibratory sensation and position.

Fourth, astereognosis.

Fifth, sensory dystaxia.

Sixth, pain and paresthesias.

Seven, hyporeflexia or arreflexia.

Eight, urinary incontinence, constipation, and impotence.  And nine, Romberg’s sign.

 

What are the regions of the spinal cord affected in tabes dorsalis?

  • Fasciculus gracilis, T6-S5, and fasciculus cuneatus, C2-T6.  It also includes the dorsal roots. 

Let’s take that again.  What are the regions of the spinal cord affected in tabes dorsalis?

  • Please pause and list them.   Fasciculus gracilis, T6-S5, and fasciculus cuneatus, C2-T6, and also the dorsal roots.

Student doctor, what are the characteristics of a lesion to the ventral spinothalamic tract?

  • The characteristics of a lesion to the ventral spinothalamic tract include contralateral loss of light touch sensation, three to four segments below the level of the lesion.

What are the characteristics of a lesion to the lateral spinothalamic tract?

  • The characteristics of a lesion to the lateral spinothalamic tract include contralateral loss of pain and temperature sensation, one segment below the level of the lesion.

Student doctor, what are the characteristics of a lesion to the ventral spinocerebellar tract?

  • Contralateral leg dystaxia.

And what about a lesion to the dorsal spinocerebellar tract?

  • What would be the clinical features?  Lateral leg dystaxia.

All right, let’s go back and review these lesions of the spinal cord from the opposite direction.  Spastic paralysis rather than flaccid paralysis refers to what type of motor neuron lesions?

  • Upper motor neuron lesions.

A positive Babinski sign is associated with an upper or lower motor neuron lesion?

  • With an upper motor neuron lesion.

What is the disease characterized by muscle atrophy and muscle weakness without sensory loss?

  • ALS (amyotrophic lateral sclerosis). 

And what type of motor neuron lesion is involved with ALS?

  • Both actually.  It is a disease of combined upper and lower motor neuron lesions.

What disease is associated with lesions of the fasciculus gracilis, T6-S5, and the fasciculus cuneatus, C2-T6, and including the dorsal roots?

  • This is tabes dorsalis.

What lesion is associated with contralateral leg dystaxia?

  • This would be a lesion to the ventral spinocerebellar tract.

And what lesion is associated with contralateral loss of light touch sensation?

  • This would be a lesion to the ventral spinothalamic tract.

What lesion would be associated with lateral leg dystaxia?

  • A lesion to the dorsal spinocerebellar tract.

Which lesion, the ventral spinothalamic tract or the lateral spinothalamic tract, would be associated with characteristics that manifest only one segment below the level of the lesion?

  • This would be a lesion to the lateral spinothalamic tract.

What disease is associated with the following: Romberg’s sign, urinary incontinence, constipation, and impotence, hyporeflexia or arreflexia, pain and paresthesias, sensory dystaxia, astereognosis, loss of vibratory sensation and position, loss of tactile discrimination, and ipsilateral sensory deficits below the lesion?

  • This would be the dorsal column syndrome or tabes dorsalis.

What two diseases that we mentioned are both diseases of the lower motor neuron?

  • Poliomyelitis and Werdnig-Hoffman disease.

Which lesion is associated with contralateral loss of pain and temperature sensation?

  • This would be a lesion in the lateral spinothalamic tract.

How many segments below the level of the lesion would be expected with a lesion to the lateral spinothalamic tract?

  • One segment.

Now, if the lesion is to the ventral spinothalamic tract, how many levels below would you expect to find manifestation of that lesion?

  • Three to four segments below.

And what would be the characteristic?

  • Contralateral loss of light touch sensation for lesions to the ventral spinothalamic tract

 

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