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Neuroscience Case Studies KINS 8210. Scenario 1.
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Scenario 1 Mr. Jones has been bothered by stiffness in his right leg for a week or so. He went out to his backyard to get into his hot tub, thinking that the warm bubbly water would relax his tense muscles. When he went to get into the water, he scalded the skin on his left foot and ankle because he did not initially notice how hot the water actually was. He did notice the temperature when he reached down with his left arm to stabilize himself as he climbed further into the tub. He then had to turn down the temperature wand wait awhile before he could continue. A long soak in the hot tub did help his stiffness but the burn is still there.
Scenario 1 Possible Answer • The boldface portions of the question are relevant to this particular answer. 'Stiffness' in the right leg suggests some degree of spasticity, which is a consequence of upper motor neuron damage; the problem may be in the left motor cortex, the left thalamus, the right medulla, or the right spinal cord. • 'Scalding' of the left foot suggests a lack of pain or temperature sensation; the problem may be located in the pain receptors of the left leg, the sensory 'pain' inputs to the left spinal cord at the lumbar level, the midline grey matter of the lumbar spinal cord, the right anterolateral pathways beginning in the lumbar levels, the right medulla, the right thalamus or the right somatosensory cortex. • Pain, temperature, touch, & motor functions of the left arm seem to be OK, suggesting that these pathways are intact; the lesion must be located below the C5-T1 (brachial plexus) level.
That gets us close to the answer, but doesn't explain why Mr. Janus retains the abilities of pain & touch sensation and motor control in the right arm. We have to look further into the segmental anatomy of the spinal cord. Ah, ha! We see that damage to the anterolateral spinal cord below the brachial plexus may result in interruption of the ascending anterolateral pathways and the decending motor output pathways while preserving the ascending sensory pathways from the arms. • Answer: The only site common to these symptoms is in the thoracic region of the Right spinal cord.
Scenario 2 Ms. Georgia is a cashier at a local grocery story. She likes her job because she gets to see all the townspeople on a regular basis. Her job requires her to stand all day; this has not been a problem until lately. She recently has been noticing difficulty with standing on her feet all day. First of all, when she tries to step into her cubicle, she feels like she is dragging her right leg after her like a sack of potatoes. Then she feels like she’s standing on a stump all day after she gets it into place. Luckily, her right side is farthest from the customers and the conveyor on which the food travels, so she can lean away from the problem, and use her counter for support. Her other concern is that she has gotten several cuts on her left leg lately , from the metal corners under her counter where the grocery bags are stored. She hasn’t noticed these injuries until she takes off her hose and realizes they are ruined.
Scenario 2 Possible Answer • The boldface portions of the question are relevant to this particular answer. Her right leg 'drags' suggesting a motor output problem; may be located in the left cortex, left thalamus, right medulla, right spinal cord (rubrospinal pathway), or lower motor neurons supplying the right leg. • Her right leg seems numb and unresponsive to stimuli ('like a stump'), suggesting a sensory input problem related to touch and pressure sensation; the problem may be located in the touch and/or pressure receptors of the right leg, these sensory inputs to the right spinal cord at the lumbar level, structures of the dorsal horn in the lumbar spinal cord, the right dorsal column pathways beginning in the lumbar levels, the left medulla (medial lemniscus pathway), the left thalamus or the left somatosensory cortex. • Her left leg was injured without her awareness, suggesting a sensory input problem related to pain transmission or perception; the problem may be located in the pain receptors of the left leg, the sensory 'pain' inputs to the left spinal cord at the lumbar level, the midline grey matter of the lumbar spinal cord, the right anterolateral pathways beginning in the lumbar levels, the right medulla, the right thalamus or the right somatosensory cortex. • Answer: The only site of injury common to these symptoms is at the thoracic levels of the Right spinal cord.
Scenario 3 Peter likes to play golf. Usually he is a very competitive member of his foursome, but his game has been off lately. He has been unable to maintain his well-practiced grip on his favorite clubs (particularly with his right hand), causing the club to slip out of alignment as he begins his swing. Additionally, as all great golfers know, maintaining visual contact with the ball is critical to accurate placemlent of the ball on the green. Peter has begun to complain that he sometimes sees two balls, and that occasionally he swings at the ‘wrong’ one. He has been unable to keep his eyes on the ball as he swings and he has not been able to watch it as it sails to its destination. Today has been particularly hot, and the foursome are all becoming fatigued as they near the final hole. It’s at this point that one of the partners notices that Peter’s left eye is crossed.
Scenario 3 Possible Answer • The boldface portions of the question are relevant to this particular answer. Left eye is crossed (diplopia); an inability to move the Left eye laterally suggests improper function of the Left lateral rectus muscle, which is innervated by the Left abducens nerve. • Right hand loses grip & slips; possible involvement of motor output pathways (Left corticospinal pathway in brainstem crosses to become the Right corticospinal pathway in the spinal cord). • Note that this set of symptoms involves ipsilateral cranial nerve signs and contralateral body signs. • Neurologic symptoms often become worse when the individual becomes fatigued or ill. • Answer: The only site common to these symptoms (involvement of the left abducens nerve and motor output pathways to the right side of the body) is the Left pons. This is one of the three possible sites where 'alternating hemiplegia' is a possibility.
Scenario 4 Ms. Pearl is a makeup specialist for a major department store. Recently, she has been having trouble at the store; she has found herself losing her balance as she cruises around the counters; she also can't locate customers when they call to her for assistance. She has also had difficulty finding items on shelves, often reaching for an item she sees, and missing the jar or bottle. Additionally, she has had to avoid lifting open bottles from the counter with her left hand because when she does, the bottle begins to shake, and spills all over the place. She used to look forward to eating out for lunch, but lately she has lost interest in eating, complaining that the food is prepared poorly and is cooked too much, making it hard to chew. Problems at home have also begun. She has had a problem getting her own makeup on evenly. The left blush and eye shadow seems darker, and has to be redone several times. Her left chin and forehead also seem to sag. When she puts on her pantyhose, the right leg never seems to be properly adjusted. This is especially embarrassing when she wears textured hose.
Scenario 4 Possible Answer • The boldface portions of the question are relevant to this particular answer. The combination of 'losing her balance' and an inability to 'locate customers when they call' suggests the vestibulocochlear nerve (c.n. VIII) may be involved. • 'Reaching for objects and missing them' and her 'shaking left hand' suggests involvement of the motor systems; perhaps the basal ganglia (Parkinson's disease) or the cerebellum (intention tremor). Note that the cerebellum physically is adjacent to the pons, while the basal ganglia are far more anterior structures in the brain. On the other hand, these tremors tend to be bilateral. Perhaps there is unilateral damage to cerebellar pathways (e.g., the cerebellar peduncles)? • Ms. Pearl reports that she finds her food 'poorly prepared' and 'hard to chew' her food. Damage to the trigeminal nerve (c.n. V) leads to weakness and wasting of the jaw muscles, and to asymmetric chewing if the damage is unilateral. Damage to the facial (c.n. VII) and glossopharyngeal (c.n. IX) nerves would impair taste sensation. • Her difficulty applying makeup evenly may also be related to impairment of trigeminal nerve function; this cranial nerve also conveys cutaneous and proprioceptive sensation from the face and mouth. • "Sagging" of her chin & forehead may be due to a reduction in tone of muscles serving these structures, suggesting involvement of the facial nerve (c.n.VII; flaccidity results from lower motor neuron injury)
Difficulty adjusting the hose on her right leg. OK, I'm willing to admit when an answer stumps me. Several friends who wear hose regularly tell me that one uses proprioception and touch to evaluate the 'evenness' of one's hose when dressing. In that case, these pathways will travel to the brain on the right side of the body, crossing over to the left side of the brain in the lower medulla and continuing as the medial lemniscus on to the thalamus. • Loss of touch and proprioceptive sensation from the right leg may be due to spinal cord injury, but a brainstem source is more likely given the other symptoms. Since the right leg is affected, we'd expect the problem to be with the medial lemniscus on the left side of the brainstem. It's a bit harder to explain the 'shaking left hand,' until .... • ... we see that the cerebellar peduncles (providing proprioceptive sensory input and motor output from the cerebellum) are located in this region of the pons, as are the trigeminal (c.n. V), facial (c.n. VII), and vestibulocochlear (c.n. VIII) cranial nerves. The glossopharyngeal nerve (c.n. IX) is not likely to be involved as it is located in the medulla. You might note that we haven't mentioned involvement of the abducens nerve (c.n. VI), which innervates the lateral rectus muscle of the eye and controls abduction. Perhaps this region has been spared, perhaps Ms. Ribbons neglected to mentioned any problems, or perhaps there was a problem which did contribute to her 'missing when reaching.' Further clinical assessments would be appropriate. • Answer: The only site common to these symptoms (involvement of both cranial nerves and spinal pathways) is the Left pons.
