The NNI stuff from Charanya:

The black tract: corticospinal/pyramidal tract which decussates at the brainstem before synapsing at the anterior horn cells at their respective spinal levels

The blue one: Spinothalamic

Okay case scenario1: Patient comes in for weakness of the biceps

So, is it a NERVE or a NERVE ROOT problem?

Nerve: Musculocutaneous nerve C5-7 (mainly C5)

What other nerves have C5? That will be the axillary nerve (C5, C6)

Which means if its a musculocutaneous nerve problem, deltoids weekness and regimental badge sign will be absent

If its a nerve root problem, then biceps weakness will be accompanied by deltoids weakness (abduction) and regimental badge sign

Case Scenario 2:

If a patient presents:

- flccidity of the LL

- upgoing plantars

The lesion is probably in the conus medullaris where both spinal cord and peripheral nerves exist and may present as such

Case scenario 3:

Patient presented with hemiparesis without facial involvement:

1. Spinal cord or brainstem lesion below level of pons (where CN*VII nerves are)

2. Cortical lesion of motor cortex sparing the region responsible for facial motor (facial nerve UMN)

General Thought Flow:

Patient with right hemiparesis:

Q1: sensory loss on the Left side?

- Yes: spinal cord lesion, Brown Sequard

- No: above

Q2: cranial nerve lesion?

- Yes: brainstem lesion. Gauge the site wrt Cranial nerves involved. Do jaw jerk

- No: higher up or below the level of exiting cranial nerves (e.g. caudal medulla)

Q3: Aphasia, neglect, visual deficits

- Yes: cortical lesion

- No: subcortical or caudal brainstem lesion