Question

A. Iva Ertarm is admitted complaining of a numb right arm. When tested, she is unable to feel when her hand and arm are touched lightly, but can still feel a hard pressure. It is determined she must have a lesion or damage within her spinal cord. Which specific pathway is affected (4 pts)? How do you know it is that specific pathway (Apts)? Which side of the spinal cord is the lesion and which funiculus must! the lesion be located (4 pts)? How do you know the specific funiculus and the side (where does it decussate) (4pts)? What is the signal direction within this pathway and what is the final destination of this information (2 pts)? 2 pts for essay formatting, grammar, spelling. Be specific in your answers.

Answer 1

The dorsal column pathway is affected.  

• It is the pathway which carries, fine touch . So iva eartarm's dorsal column pathway may be affected.  
• Her crude toch is restored so her ventral spinothalamic tract is not affected.  
• Dorsal column pathway carries fine touch, proprioception, vibration, two point discrimination.
• Spinothalamic tract carries crude touch , pain , temperature .
• The lesion is on the right side of the spinal cord .
• It is because her right arm is affected .
• The lesion must be located in the cuneate funiculus of the spinal cord , it is the posterior funiculus of the spinal cord.  
• dorsal column pathway donot decussate at the level of spinalcord.
• They Decussate at the level of medulla and form medial lemniscus .
• Thus if the lesion is on spinal cord, then surely the lesion will be on same side of spinal cord. If right limb is affected then lesion would be on right side of the spinal cord.
• The Cuneate funiculus is affected because dorsal column sensory signals from upper half of the body pass through cuneate funiculus in the spinal cord.
• If lowerlimb is affected then gracillis funiculus would be affected since lower limb dorsal column sensory signals travel through gracilis funiculus .
• Talking about dorsal column pathway , it has 3 order of neurons first order neurons are located in dorsal root ganglion. it is a pseudounipolar neuron where one axon splits into two , where one goes to periphery to carry information and other ascends  along dorsal column . the one wich ascends travel through posterior funiculus in the spinal cord and they reach the medulla in the medulla they relay on second order neurons in the medulla whose axon decussate and cross over the other side forming the medial lemniscus . these axons of 2nd order neuron carries information to the thalamus where they relay on 3rd order neuron in the thalamus . These axons of 3rd order neuron finally transmit signals to the primary somatosensory area of cortex.