Julie Lee MBB PBL Case #2: “Jerry and Chuck” Where is the lesion? Julie Lee MBB PBL Case #2: “Jerry and Chuck”

Our patient, Mr. Jerry Yung, is a 67 year old male that presents with a host of symptoms, as we will soon review. Where is his lesion?

“His right pupil is 2mm and his left pupil is 4mm in a well-lit room “His right pupil is 2mm and his left pupil is 4mm in a well-lit room. When the room is darkened, his right pupil stays about 2mm, and his left dilates to 8mm. With bright light, both pupils constrict to 1mm. His right eyelid seems droopy.” Horner’s syndrome: combination of signs and symptoms caused by disruption of the sympathetic nerve supply to the eye

Pupillary dilation is controlled by the descending excitatory pathway that originates in the hypothalamus. The pathway extends through the posterior hypothalamus and the lateral portion of the brainstem to the upper spinal cord. It then connects to the preganglionic segment that bridges the spinal cord to the sympathetic chain, where it synapses in the superior cervical sympathetic ganglion. Finally, the postganglionic segment traverses the remainder of the pathway via the internal carotid arteries and V1 to the pupillodilator muscle.2 Sympathetic innervation to the eye (specifically the pupillodilator muscle) Image: http://www.ib.cnea.gov.ar/~redneu/2013/BOOKS/Principles%20of%20Neural%20Science%20-%20Kandel/gateway.ut.ovid.com/fulltextservice/ct%7B06b9ee1beed594190674f1983457a7dd32af6a0d5a4c9892~53/da7c45ff14.gif.png

anhidrosis ptosis miosis Shows the branches of the 3rd neuron (aka the postganglionic segment) and the other sympathetic effects. We did not observed anhidrosis in our patient, although it is an associated symptom of Horner’s. Image: http://nervestudy.com/wp-content/uploads/2013/04/Horners.gif

Where’s the lesion? The lesion could be anywhere along this tract that begins at the hypothalamus through the preganglionic segment and finally the postganglionic segment before it branches. Image: http://www.ib.cnea.gov.ar/~redneu/2013/BOOKS/Principles%20of%20Neural%20Science%20-%20Kandel/gateway.ut.ovid.com/fulltextservice/ct%7B06b9ee1beed594190674f1983457a7dd32af6a0d5a4c9892~53/da7c45ff14.gif.png

“At rest, his eyes are moving back and forth, and they appear to conjugately move slowly to the right before jerking more quickly to the left.” Left-beating nystagmus Suggests a right-sided vestibular lesion Also note that the patient expressed that he felt “dizzy” and nauseous when he tries to stand up or walk, which further supports the presence of a vestibular lesion.

Left Right Loss of function in the right side of the vestibular system due to a lesion is equivalent to the activation of the left vestibular semicircular canals. Image: http://cnx.org/resources/12865f8120d7c4f131ee687cf17c50c4/1419_Vestibulo-Ocular_Reflex.jpg

Left Right Where’s the lesion? Anywhere from the semicircular canals to the vestibular nerve, which terminates on the neurons of the ipsilateral vestibular nucleus. http://cnx.org/resources/12865f8120d7c4f131ee687cf17c50c4/1419_Vestibulo-Ocular_Reflex.jpg

Image: http://www.nature.com/gimo/contents/pt1/fig_tab/gimo2_F3.html

“…when you touch his right face, he feels it less than on the left “…when you touch his right face, he feels it less than on the left.” Impairment of CN V facial sensation Suggests a right-sided trigeminal lesion

Images: http://o.quizlet.com/i/mqB6AWVy0bWdPo4RUeQ-TQ.jpg http://o.quizlet.com/i/wpmMez1rDUK0NZ351VkQ-A.jpg

“…difficulty hearing you softly whisper into his right ear” Unilateral hearing loss in right ear

Where’s the lesion?  Localizing lesion! The lesion must be on or between the right cochlear nerve of CN VIII and the cochlear nuclei. A lesion beyond this would not produce a unilateral hearing loss, because both ears become bilaterally innervated past the cochlear nuclei.  Localizing lesion! Image: http://what-when-how.com/wp-content/uploads/2012/04/tmp15F73.jpg

“…light touch on the left arm and leg seems different compared to the right” Impaired anterior spinothalamic tract, responsible for light/crude touch and pressure

Lesion is hypothesized to be on the right, so it makes sense that the left side of the body has impaired sensation due to the crossing of neurons that occurs at the anterior white commissure before ascending in the anterior spinothalamic tract. Images: http://www.cixip.com/Public/kindeditor/attached/image/20121026/20121026104445_18586.jpg http://www.cixip.com/Public/kindeditor/attached/image/20121026/20121026104420_26275.jpg

“He has trouble accurately touching your finger with his right finger and is unable to smoothly trace a line with his right heel” and “he staggers from side to side” whenever he tries to stand up Ataxia resulting from a cerebellar lesion

Image: http://www. cixip

putting it all together Positive exam findings Horner’s syndrome on the right Left-beating nystagmus* Impaired facial sensation on the right Unilateral hearing loss of right ear* Impaired touch sensation on the left side of body Ataxia *(pretty darn) localizing

Vestibular nuclei (all four) are located on the floor of the fourth ventricle, dispersed between the medulla and pons. Cochlear nuclei are located on the dorsolateral surface of the brainstem at the junction of the medulla with the pons. Image: http://www.nature.com/gimo/contents/pt1/fig_tab/gimo2_F3.html

Cross section of the rostral medulla Does the localization fit with the rest of the clinical picture? Descending sympathetic tract Image: http://what-when-how.com/wp-content/uploads/2012/04/tmp14119_thumb.jpg

what about the negative findings? “His facial movements are symmetric other than his right eyelid drooping” → motor functions of CN VII intact “His tongue is in the midline and his palate elevated symmetrically” → CN XII intact “Correctly identifies pin touches and is able to correctly tell you which direction you move his fingers and toes” → lateral spinothalamic tract (pain, temperature), dorsal column (discriminative touch, proprioception, pressure, vibration) intact “…his reflexes are normal and his toes are going down bilaterally” → negative UMN lesion Motor nucleus of CN VII is located in the pontine tegmentum; therefore, lesion to the lateral medulla, would have no effect on innervation of facial muscles, which is what we observe Nucleus of CN XII is located in the medulla along the midline and therefore not affected by a lateral lesion, which is what we observe Dorsal column functions (proprioception) are intact, as the pathway runs along the medial lemniscus in the medulla, which fits into the hypothesis for where our lesion is. While we would expect that the lateral spinothalamic tract would also be impaired as we observed the anterior spinothalamic tract to be, perhaps the tract is more resistant to damage and therefore we do not see effects of its disruption quite yet? The corticospinal tract would run along the medullary pyramid and not be affected by a lateral lesion, which the lack of UMN lesion symptoms in our patient.

references Kritchevsky, M. (2014). Mind, Brain, and Behavior II Syllabus. Riordan-Eva, P., Hoyt, W.F. (2011). Chapter 14. Neuro-Ophthalmology. In Riordan-Eva P, Cunningham E.T., Jr (Eds), Vaughan & Asbury's General Ophthalmology, 18e. Retrieved January 13, 2015 from http://accessmedicine.mhmedical.com/content.aspx?bookid=387&Sectionid=40229331.