Clinical Pearls in Neuro

Ever heard of nerve root concussion

[FONT=&amp] A 55-year-old patient is involved in a severe motor vehicle accident and admitted to the emergency room. The patient complains of abnormal sensations such as burning and tingling in the left arm. A neurological examination further reveals little change in motor or other sensory functions. Which of the following regions was most likely affected by the accident?[/FONT]

[FONT=&amp]A. Dorsal horn of the spinal cord[/FONT]
[FONT=&amp]B. Ventral horn of the spinal cord[/FONT]
[FONT=&amp]C. Ascending pathways in lateral funiculus of the left spinal cord[/FONT][FONT=&amp]
D. Dorsal columns of spinal cord[/FONT]
[FONT=&amp]E. Nerve roots associated with the cervical cord[/FONT]

[FONT=&amp]EXPLANATION:
[/FONT]
The pain and paresthesia experienced by the patient in the upper left arm is most likely the result of a moderate concussion of the nerve roots associated with the dermatomes in that limb. The concussion was severe enough to generate these abnormal sensations but not sufficiently devastating to cause complete sensory loss in the limb. Damage to the dorsal horn would cause loss of pain and temperature sensation, as well as affecting tactile sensation; likewise, damage to the lateral funiculus would cause loss of pain and temperature sensation associated with the right limbs; the ventral horn mediates motor functions and is thus unrelated to this disorder; the dorsal columns mediate signals associated with conscious proprioception, but not pain.


[FONT=&amp]The answer is E.[/FONT]


comments - wondering why the motor component was not affected by the cocussion ?

Ans - becos they have better cushioning and are thicker and sturdier ( even though they travel in the same nerve bundle ) and hence are more resistant to concussion.

(-:

 

Self Assessment question to remember the various structures innervated by mandibular nerve

A 73-year-old man presents because of repeated biting of his tongue and cheek, and difficulty chewing. The left side of his tongue is somewhat swollen and he has two different cuts on it. His left cheek is slightly less full over the angle of the mandible compared to the right side. He has very little sensation over his left mandible, along the side of his head, and on the left side of his tongue. He has weakened ability to elevate his mandible on the left side. Taste sensation on his tongue is normal. He also complains of slight dryness on the left side of his mouth. The rest of his cranial nerve examination is normal. A head CT is ordered because his physician suspects which one of the following?

A. A tumor at the left superior orbital fissure
B. A tumor blocking the left foramen rotundum
C. A tumor blocking left foramen ovale
D. A tumor blocking the left internal acoustic meatus
E. A tumor blocking the right internal acoustic meatus


EXPLANATION:

It is suspected that a tumor is blocking the left foramen ovale. The mandibular division of the trigeminal cranial nerve exits the skull through the foramen ovale. This division provides general sensation to the tongue (via the lingual nerve) and mandibular teeth (via the inferior alveolar nerve) and area over the mandible (via the buccal nerve). In addition, the mandibular division of the trigeminal also innervates eight muscles (the four muscles of mastication [temporalis, masseter, medial, and lateral pterygoid muscles], two associated with the floor of the mouth [the mylohyoid and anterior belly of the digastric muscles], and two tensors [tensor tympani in the middle ear and tensor veli palatini in the soft palate]).

In addition, preganglionic nerves from cranial nerve IX (via the lesser petrosal nerve) also pass through the foramen ovale on their way to stimulate the parotid salivary gland. A tumor at the superior orbital fissure (answer a) would affect eye movements and forehead sensation.

A tumor at the foramen rotundum (answer b) would affect sensation under the eye on the face and maxillary teeth pain.

A tumor at the internal acoustic meatus (answers d and e) would affect the facial nerve, hearing, and balance.

Ans C

(Y)