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The greater occipital nerve innervates posterior neck muscles and the skin of the posterior surface of the scalp. Damage to this nerve does not explain the patient's inability to raise her shoulder and would also manifest itself as numbness in the skin of the posterior surface of the scalp.
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The spinal nerve C3 is formed by the dorsal and ventral roots of C3. Although branches from the ventral primary rami of both C3 and C4 combine with the accessory n. to form the subtrapezial plexus, C3 and C4 provide only proprioception to the trapezius muscle. Damage to either spinal n. C3 or C4 would have no effect on the motor function of the muscle as to raising the shoulder.
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The dorsal scapular nerve innervates rhomboideus major, rhomoboideus minor, and the lower portion of levator scapulae. Injury to this nerve would weaken the ability of the rhomboids to assist the trapezius in retracting the scapula to the midline on the affected side. Injury to this nerve would not affect the patient's ability to raise her shoulder.
Our second question was why the patient had no numbness in this case. We learned that the reason for that is the spinal accessory never (CN XI) is a unique peripheral nerve. It is truly an only motor nerve that does not carry any sensory fibers whatsoever, thus, patient had no sensory numbness when the trapezium muscle contracts. Most other motor nerves of the upper limb, such as the ulnar nerve, and most nerves to skeletal muscle, all carry cutaneous sensory nerves that innervate sweat glands (secretomotor neurons), blood vessel walls (vasomotor neurons), and arrector pili muscles (pilomotor neurons). Some other motor nerves (e.g., dorsal scapular nerve) do not carry any cutaneous sensory neurons; however, all nerves of skeletal muscle carry proprioceptive fibers. These fibers transmit sensory information concerning the state of contraction and position of joints to the central nervous system, allowing for coordination of movement. That’s why the patient felt the drop of the affected shoulder.
The third and fourth questions were what sequence of anatomical pathway the spinal accessory nerve executes coordinated movement of the trapezius muscle. We found that the spinal accessory nerve exits the skull through the jugular foramen, and travels deep to the sterocleidomastoid muscle (SCM), which it innervates. As the accessory nerve emerges from under the SCM, it combines with spinal nerves C3 and C4, which carrying proprioceptive fibers, at C5 level to form the subtrapezial plexus.(p.676) The combined nerve is then traverses the posterior triangle obliquely to innervate the trapezius muscle, which is the only muscle that can elevate the tip of the shoulder (the acromion).
Case 2
Case Summary:
Patient brought into the ER with a high fever, lethargy, and a stiff neck, upon examination, the physician suspect meningitis, the diagnosis is confirmed by bacterial growth in the cerebrospinal fluid (CSF) extracted by lumbar puncture. Patient was successful recover without any complications.
Terms:
Lumbar puncture: is a procedure to collect and examine the cerebrospinal fluid (CSF) surrounding the brain and spinal cord. During a lumbar puncture, a needle is carefully inserted into the spinal canal low in the back (L4-L5) region. Sample of CSF are collected and studied for diagnose purpose against life threatening diseases. It is also sometimes used for therapeutic purposes, such as injecting anesthetics or medicines into the CSF, or injecting dye into the CSF for identifying disc problems on X-ray pictures. This procedure is also referred as a spinal tap.
Lethargy: the quality or state of being drowsy, dull, listless and unenergetic.
Case Discussion:
In class, our group discussed about Case 2. Our first question was how to locate the puncture site. We learned that on average, the spinal cord ends at the L1 – L2 level. To insure the safety and not puncturing the spinal nerves, it is suggested to insert the needle between L3 to L4 or L4 to L5. The land mark used to locate the site is the superior iliac crests. The line connecting the left and right iliac crest points usually passes through the spinous process of the L4 vertebra, thus, by feeling the indentation of the interlaminar spaces, we can locate the puncture site.
The next question we discussed was why the syringe needle is inserted in the midline and with the median plane and what structures that the needle traverses before entering the lumbar cistern. We learned that at the level of the lumbar cistern the nerve roots are suspended in CSF and fixed by dural sleeves laterally. Thus, it is necessary to insert the needle through the interlaminar space in the midline to avoid damage to nerve roots. The layers that the needle must pass through before reaching to CSF containing subrachnoid spaces are: skin, superficial fascia, supraspinous ligament, interspinous ligament, ligament flava, epidural space, dura mater, subdural space and arachoid mater.
The third question was what position the patient is placed in during this procedure. We found out that the patient is usually lying on the side, while flexing his or her back in the fetal position; this increases the spaces between the spinous process and lowering the chance of accidental damage to the spinous nerve. (See picture above)
The fourth question suggested the patient complains of a severe headache after the procedure. We discussed the possible reasons that might cause this complication is the dramatic decreasing in pressure of subarachnoid space as the physician withdrew CSF out. This sudden decrease in pressure although small, but would cause the brain to sag a bit and stretches the dura. The dura mater contains a rich amount of pain receptors that respond to stretch and tension, thus, in turn causes severe headaches. To prevent this, the patient is usually asked to lay down with the head at a slightly lower level than the body.
The last question we discussed other situations that would require a lumbar puncture. We found that this procedure may also be used for therapeutic purposes, such as injecting anesthetics or medicines into the CSF, or injecting dye into the CSF for identifying disc problems on X-ray pictures.
Case 3
Case Summary:
A newborn infant has normal vital signs, however has a bulging cyst-like structure approximately 4cm in diameter protruding from back. He also shown limited movement of the lower extremities and that both feet are plantarfelxed and inverted at the ankle.
Terms:
Plantarfelx: to flex the foot or toes toward the sole.
Case Discussion:
In class, our group discussed about Case 3. First we identified the patient suffer from spina bifida. This is a congenital neural tube defect that the vertebral column is split in the midline. Most neural tube defect involve an abnormality of the neural arch and can be associated with a variety of structural involvements which can include the meninges, spinal cord, and can vary according to the site at which closure of the tube fails to occur. Neural tube defects occur average one in every 1000 births and the incidence varies with regard to geography, ethnicity, and other factors.
Next we researched on the types of anatomical structures can be involved with spina bifida. Typically, spina bifida is one or more vertebrae lamina fail to fuse, mostly in the lumbar region. In our case, patient developed Spina bifida cystica as a result of the failure of closure of one or more vertebral arches, and frequently this condition allows the herniation of meninges and/or spinal cord.
The third question reviews various types of neural tube disorders and their presentation. From previous courses, we learned that similar neural tube disorders like Anecephaly the incomplete closure of the skull and Spina Bifida occulta the reveal a tuft of hair over the spinal process. The types of neural tube defects vary according to the structures that are compromised:
- Myelomeningoceles - involving the spinal cord and meninges
- Meningocele - involving just vertebral arch formation with an outward bulging of the meninges and a normal spinal cord
- Encephalocele - involvement of the posterior cranium with herniation of brain contents through the opening
- Anencephaly –involving the failure of the cranial portion of the neural tube to close, with associated cranial vault malformation.
Next, we explored the cause of spina bifida. It is a congential defect that causes the failure of neural tube closure at around 4 weeks gestation during embryological development, resulting in an “open” vertebral canal.Other complications are associated with spina difida, are possible partial or full paralysis of lower extremity, hydrocephalus and mental handicap. Currently, the most popular prophylactic therapy for prenatal prevention of spina difida is dietary supplement ingestion of folic acid.
Case 4
Case Summary:
Physicians find an 82 year old man unconscious and in cardiac arrest after a fall. They successfully revived the patient to normal sinus rhythm using ACLS protocols, but the patient remains profoundly unconscious. After immobilize patient spine and transport to hospital for further examinations, discovers the patient suffer from C1 and C2 fractures with spinal cord injury that resulting in quadriplegia. T2 –T4 spinous processes and several left ribs are also fractured. The patient never regains consciousness and died the following day.
Terms:
Sinus rhythm: is the normal beating of the heart, usually measured by an electrocardiogram.
ACLS: refers to Advanced Cardiac Life Support, which is a set of clinical interventions for the urgent treatment of cardiac arrest, stoke and other life threatening medical emergencies.
Quadriplegia: also known as Tetraplegia is a medical condition where paralysis of four limbs is caused by illness or injury to the spinal cord in the neck (cervical area).
Case Discussion:
In class, our group discussed about Case 4. First we try to find the function of the dens of C2, and its importance upon damaging. The den, also called the odontoid process, is the portion of the axis C2 about which the C1 and the head rotate. Because the den extends superiorly into the ring of C1, it is subjected to shear forces and fracture from C1 in neck injuries. The dens can then impact the spinal cord, injuring or severing it. In this case, although the patient's spinal cord was not severed, impact from the dens caused a spinal cord hematoma resulting in quadriplegia.
Next we discussed the reasons for physicians to immobilize the patient’s spinal before transporting to hospital. It is because after trauma, especially for any vertebra fracture that has the potential to injure the spinal cord, fixing the spine can prevent uncontrolled movement of potentially fractured vertebrae. Vertebral fracture can cause spinal cord injury; spinal cord injury then can cause paralysis or death.
Conclusion:
Through learning the materials from the lectures about human back and its associated clinical cases, I learned that spinal cord acted as a nerve highway that transmits signals from the controlling center brain to every part of the body. Its especial structure maximized the protection against tension and forces, at the same time, allowed for the wide distribution of the nerves spread to all organs of the body. Upon damaging to the supporting structure, the spinal vertebrae will cause various distresses on the nerves it protects. Physicians based on the specific symptoms and its association with the functions of nerves, were able to identify the causes and provide treatments. In this course, I was most fascinated by the lumbar puncture and it’s widely usage in diagnoses and therapeutic treatments
Reference
CMU lab manual for student.
Gray’s Anatomy book
http://www.wikipedia.com
www.spinal-injury.net/
www.webmd.com
www.apparelyzed.com/spinalcord.html