A 29 year old patient was investigated at the neurology clinic, and it was noted that she lacks the two point discrimination ability in her left hand. What is the most likely cause of such a presentation:

Correct Answer: C

Rationale: Medial lemniscus lesion in the right side of the pons . Two-point discrimination (fine touch) from the left hand travels via the fasciculus cuneatus (upper limb) on the left side, decussatin the medulla as the medial lemniscus, and ascends on the right side to the thalamus. A right pons lesion in the medial lemniscus disrupts this crossed pathway, causing left-hand deficit. Choice A (right C2) affects the wrong side pre-decussation. Choice B (right C5) is ipsilateral, not affecting left hand post-decussation. Choice D (gracilis) is for lower limbs. Thus, C matchthe crossed pathway disruption, making it correct.

Correct Answer: C

Rationale: Unconscious muscle joint sense travels in the anterior spinocerebellar tract . The anterior spinocerebellar tract carriunconscious proprioception from lower limbs to the cerebellum via the superior cerebellar peduncle. Choice A is wrong (two-point discrimination is dorsal column). Choice B is incorrect (pain is lateral spinothalamic). Choice D is false (no posterior spinothalamic tract; pressure is anterior spinothalamic). Thus, C accurately pairs the sensation and pathway, making it correct.

Correct Answer: D

Rationale: The anterior spinothalamic tract terminatin the ventral posterolateral nucleus of the thalamus . The anterior spinothalamic tract (crude touch) terminatin the VPL nucleus of the thalamus, relaying to the cortex. Choice A is wrong (posterior columns end in nucleus gracilis/cuneatus). Choice B is false (spinoreticular ends in reticular formation). Choice C is incorrect (spinotectal ends in superior colliculus). Thus, D is accurate, making it correct.

Correct Answer: B

Rationale: Cervical region . The lateral corticospinal tract, controlling voluntary movement, has most fibers synapsing in the cervical region (C1-C8), innervating upper limbs for fine motor skills (e.g., hands). Choice A (thoracic) is less dominant. Choice C (coccygeal) and D (lumbar) target lower body, with fewer fibers. Thus, B reflects the tracts primary focus, making it correct.

Correct Answer: D

Rationale: Tectospinal tracts. The tectospinal tract, from the superior colliculus, coordinathead and neck reflexto visual stimuli (e.g., tracking). Choice A (rubrospinal) is for tone. Choice B (vestibulospinal) is for posture. Choice C (spinothalamic) is sensory. Thus, D correctly identifithe tectospinal role, making it correct.