Category Archives: Neurosurgery

Glasgow Coma Scale (GCS)

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BUY THIS AS A STUDY CARD

The Glasgow Coma Scale is a scoring system used to evaluate someone’s level of consciousness. It is scored out of 15 with 15 being totally awake and alert and 3 being totally not.

The important thing to remember is that the lowest score possible is 3.

Absolutely anything can score a 3, however if you are a living, breathing human being, hopefully you are scoring well up into the 10s.

Generally the GSC is applied in trauma situations and can be used as part of the decision making process of such thing things like should this patient be intubated?

  • ≥13 correlates with mild brain injury (or being ok)
  • 9-12 correlates with moderate injury
  • ≤8 represents severe brain injury – you should probably consider intubating them as they most likely cannot protect their airway
Thanks to Mike for the guest doodle!

DANGER ZONE!!! (the cavernous sinus)

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The danger zone on the face is a little triangle from the corners of the mouth up to the bridge of the nose. The reason it has such an epic name is because due to its venous drainage (from the facial veins and pterygoid plexus) there’s the possibility of infection traveling from that area into the cavernous sinus.

The cavernous sinuses (there’s one on each side) is an area posterior to the maxillary sinuses and lateral to the pituitary. It receives blood from the superior and inferior ophthalmic veins, superficial cortical veins and the basilar plexus. The blood then drains into the petrosal sinuses (you guessed it, there’s a superior and inferior one of those too) and then those drain into the internal jugular vein.

The thing about the cavernous sinuses a whole lot of important stuff passes through it.

  • CN III (occulomotor)
  • CN IV (trochlear)
  • CN V1 (ophthalmic branch of trigeminal)
  • CN V2 (maxillary branch of trigeminal)
  • CN VI (abducens)
  • Internal carotid (and the sympathetic fibres on the carotid)

This means that if you are so unfortunate as to have infection tract back into it, there can be some nasty consequences like meningitis and cavernous sinus thrombosis which will generally present as problems involving those nerves.

The abducens and carotid are more medial and thought to be more bathed in the warm loving venous drainage meaning these are generally the first to show signs of a problem a-brewin’.

Find that lesion! (deep tendon reflexes of the arm)

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The arm has too many muscles. It also has too many nerves.

The problem is that someone comes in with weakness or numbness and you need to think, “Where in the brain/spine/nerve root/bits of brachial plexus/terminal branch is the actual problem?!”

One of the ways to help suss this out is by testing the deep tendon reflexes.

  • Only biceps reflex absent – might be problem with musculocutaneous nerve or C5
  • Both brachioradialis and triceps absent – problem with the radial nerve
  • Only triceps absent – potential problem with C7

Of course you should correlate the reflex findings with the sensory findings and motor strength (remember the good old ASIA exam for testing specific nerve roots) to help determine if it is a terminal branch issue or something higher up.

And don’t forget to grade those reflexes!

Grade Description
0 Absent
1+ Diminished
2+ Normal
3+ Brisk
4+ Very brisk +/- Clonus

Generally upper motor neuron (UMN) lesions result in hyperreflexia while lower motor neuron (LMN) lesions result in hyporeflexia.

Median Nerve Distribution

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The median nerve provides sensory and motor innervation to the anterior compartment of the forearm and hand.

  • Motor branches
    • Pronator teres
    • Flexor carpi radialis
    • Flexor carpi sublimis
  • Anterior interosseus (motor)
    • Flexor pollicis longus
    • Flexor digitorum profundus to 2nd & 3rd fingers
    • Pronator quadratus
  • Palmar cutaneous
    • Sensory distribution: Skin over thenar eminence
  • Terminal motor
    • Abductor pollicis brevis
    • Opponens pollicis
    • Lumbricals: 1st & 2nd
    • ± Flexor pollicis brevis: Also innervated by ulnar nerve
  • Terminal sensory
    • Sensory to palmar surface of thumb, 2nd, 3rd & lateral 1/2 of 4th finger

Physical exam for different muscles supplied by median nerve

  • Flexor digitorum superficialis: patient flexes fingers at PIP joint against resistance
  • Flexor digitorum profundus: patient flexes fingers at DIP joint against resistance
  • Flexor pollicis longus (anterior interosseous nerve): flexes distal phalanx of thumb against resistance
  • Abductor pollicis brevis: patient abducts thumb at right angles to palm against resistance
  • Opponens pollicis: patient touches base of little finger with the thumb, examiner tries to pull  apart
  • 1st lumbrical interosseous: patient extends finger at the PIP joint against resistance with the MCP joint hyperextended and fixed

Spinal Cord Syndromes

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There are 4 main spinal cord syndromes, plus 2 sort-of-spinal-cord syndromes. Some are not common, but a favourite of examiners because they’re just so darn cool in that they really demonstrate where things cross (like in Brown-Sequard syndrome). Cauda equina syndrome is also an important one to know because if you see it acutely, the damage can actually be temporary (otherwise the person is stuck with permanent bowel and bladder dysfunction, which is really no fun).

Muscles groups for the ASIA exam

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ASIA stands for the American Spinal Injury Association. As part of their oh-so-standardized grading for spinal injuries, they devised the muscle groups you need to test corresponding to each nerve root.