Parasympathetic sacral outflow US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Parasympathetic sacral outflow. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Parasympathetic sacral outflow US Medical PG Question 1: A 19-year-old man is brought to the emergency department following a high-speed motor vehicle collision in which he was a restrained passenger. He complains of pelvic pain and urinary retention with overflow incontinence, along with associated lower extremity weakness. Examination shows perineal bruising and there is pain with manual compression of the pelvis. Injury to which of the following structures is most likely responsible for this patient's urinary incontinence?
- A. Ilioinguinal nerve
- B. Obturator nerve
- C. Genitofemoral nerve
- D. Pelvic splanchnic nerves (Correct Answer)
- E. Superior gluteal nerve
Parasympathetic sacral outflow Explanation: ***Pelvic splanchnic nerves***
- Urinary retention with overflow incontinence and lower extremity weakness following a pelvic trauma suggests damage to the **sacral spinal segments** or the **pelvic splanchnic nerves**.
- These nerves carry **parasympathetic fibers** that stimulate bladder contraction (detrusor muscle) and relaxation of the internal urethral sphincter, which are crucial for normal micturition.
*Ilioinguinal nerve*
- This nerve supplies sensory innervation to the **genitalia** and part of the inner thigh, and motor innervation to the internal oblique and transversus abdominis muscles.
- Damage to this nerve would primarily cause sensory deficits or abdominal muscle weakness, not urinary retention or lower extremity weakness.
*Obturator nerve*
- The obturator nerve primarily innervates the **adductor muscles of the thigh** and provides sensory innervation to the medial thigh.
- Injury would result in difficulty with hip adduction and sensory loss in the medial thigh, not bladder dysfunction or diffuse lower extremity weakness.
*Genitofemoral nerve*
- This nerve provides sensory innervation to the **anterior compartment of the thigh** and the external genitalia, and motor innervation to the cremaster muscle.
- Damage would typically manifest as altered sensation in these areas or an absent cremasteric reflex, without directly affecting bladder function.
*Superior gluteal nerve*
- The superior gluteal nerve innervates the **gluteus medius, gluteus minimus, and tensor fasciae latae muscles**, which are crucial for hip abduction and stabilization during walking.
- Injury would lead to a characteristic **Trendelenburg gait**, but would not directly cause urinary incontinence or retention.
Parasympathetic sacral outflow US Medical PG Question 2: A 58-year-old obese male has noticed the gradual development of a soft bulge on his right groin that has been present over the past year and occasionally becomes very tender. He notices that it comes out when he coughs and strains during bowel movements. He is able to push the bulge back in without issue. After examination, you realize that he has an inguinal hernia and recommend open repair with mesh placement. After surgery, the patient returns to clinic and complains of numbness and tingling in the upper part of the scrotum and base of the penis. What nerve was most likely injured during the procedure?
- A. Ilioinguinal nerve (Correct Answer)
- B. Iliohypogastric nerve
- C. Lateral femoral cutaneous nerve
- D. Obturator nerve
- E. Genitofemoral nerve
Parasympathetic sacral outflow Explanation: **Ilioinguinal nerve**
- The **ilioinguinal nerve** supplies sensory innervation to the skin of the **scrotum** (or labia majora in females), the medial thigh, and the base of the penis.
- Injury to this nerve during an open inguinal hernia repair can cause **numbness and tingling** in these specific areas, consistent with the patient's symptoms.
*Iliohypogastric nerve*
- The **iliohypogastric nerve** primarily provides sensation to the skin over the **suprapubic region** and a small part of the buttock.
- Damage to this nerve would not typically result in numbness of the scrotum or base of the penis.
*Lateral femoral cutaneous nerve*
- This nerve is responsible for sensory innervation of the **lateral aspect of the thigh**.
- Its injury would lead to symptoms of numbness or pain on the lateral thigh (**meralgia paresthetica**), not the scrotum or penis.
*Obturator nerve*
- The **obturator nerve** is a motor nerve that innervates the **adductor muscles of the thigh** and provides sensory innervation to a small area of the medial thigh.
- Damage to this nerve would result in **adductor weakness** and sensory loss in the medial thigh, which does not match the patient's complaints.
*Genitofemoral nerve*
- The **genitofemoral nerve** has two branches: the genital branch (supplies the cremaster muscle and scrotal skin) and the femoral branch (supplies skin of the anterior thigh).
- While the genital branch does innervate the scrotum, injury to this nerve more commonly causes **cremasteric reflex loss** or pain radiating to the anterior thigh, and the described symptoms (base of penis) are more characteristic of ilioinguinal nerve involvement.
Parasympathetic sacral outflow US Medical PG Question 3: One day after undergoing surgery for a traumatic right pelvic fracture, a 73-year-old man has pain over his buttocks and scrotum and urinary incontinence. Physical examination shows right-sided perineal hypesthesia and absence of anal sphincter contraction when the skin around the anus is touched. This patient is most likely to have which of the following additional neurological deficits?
- A. Impaired hip flexion
- B. Paralysis of hip adductors
- C. Absent cremasteric reflex
- D. Impaired psychogenic erection
- E. Absent reflex erection (Correct Answer)
Parasympathetic sacral outflow Explanation: ***Absent reflex erection***
- The patient's symptoms (buttock/scrotal pain, perineal hypesthesia, urinary incontinence, absent anal sphincter contraction) suggest **damage to the sacral plexus and pudendal nerve**, consistent with a **cauda equina syndrome**.
- **Reflex erections** are primarily mediated by the **sacral parasympathetic outflow (S2-S4)**, which are likely compromised given the other sacral nerve deficits.
*Impaired hip flexion*
- **Hip flexion** is primarily controlled by the **L1-L3 nerve roots** (e.g., iliopsoas muscle), and while a severe pelvic fracture could cause widespread nerve damage, the current symptoms localize more strongly to the sacral region.
- The described symptoms are more indicative of **sacral nerve involvement** rather than higher lumbar segments that govern hip flexion.
*Paralysis of hip adductors*
- **Hip adduction** is mainly innervated by the **obturator nerve (L2-L4)**.
- The patient's symptoms point to **S2-S4 nerve dysfunction** (perineal sensation, anal sphincter, bladder), which are distinct from the obturator nerve's primary innervations.
*Absent cremasteric reflex*
- The **cremasteric reflex** is mediated by the **genitofemoral nerve (L1-L2)**.
- The symptoms presented are more consistent with **sacral nerve damage**, specifically S2-S4, rather than the higher lumbar segments responsible for the cremasteric reflex.
*Impaired psychogenic erection*
- **Psychogenic erections** are initiated by **supraspinal input** descending through the thoracolumbar spinal cord (T10-L2) to activate sympathetic pathways.
- While sacral nerve damage can affect the final efferent pathway for all erections, the direct impairment of psychogenic initiation is linked to higher centers and **thoracolumbar sympathetic outflow**, not purely sacral damage.
Parasympathetic sacral outflow US Medical PG Question 4: A 75-year-old man comes to the physician because of a 2-week history of sharp, stabbing pain in the lower back that radiates to the back of his left leg. He also has had a loss of sensitivity around his buttocks and inner thighs as well as increased trouble urinating the last week. Two years ago, he was diagnosed with prostate cancer and was treated with radiation therapy. Neurologic examination shows reduced strength and reflexes in the left lower extremity; the right side is normal. The resting anal sphincter tone is normal but the squeeze tone is reduced. Which of the following is the most likely diagnosis?
- A. Central cord syndrome
- B. Conus medullaris syndrome
- C. Anterior spinal cord syndrome
- D. Brown-sequard syndrome
- E. Cauda equina syndrome (Correct Answer)
Parasympathetic sacral outflow Explanation: ***Cauda equina syndrome***
- The patient presents with **bilateral sensory loss in the perineal region** (**saddle anesthesia**) and **new-onset urinary dysfunction** (trouble urinating, reduced squeeze tone), which are classic symptoms of cauda equina syndrome.
- The **sharp, stabbing radicular pain** radiating down the leg indicates nerve root involvement, characteristic of cauda equina rather than conus medullaris.
- The **asymmetric motor weakness** (left leg only) supports cauda equina syndrome, as compression can preferentially affect specific nerve roots, whereas conus medullaris typically causes more symmetric bilateral deficits.
- The history of **prostate cancer** and **radiation therapy** suggests a potential metastatic lesion compressing the cauda equina nerves.
*Central cord syndrome*
- This syndrome primarily affects the **upper extremities more than the lower extremities** and typically results from hyperextension injuries in older individuals.
- It often presents with **dissociated sensory loss** (loss of pain and temperature sensation) below the level of the lesion, which is not the primary complaint here.
*Conus medullaris syndrome*
- Affects the **sacral spinal cord segments (S3-S5)**, leading to **symmetrical motor and sensory deficits**, often with prominent early **bowel and bladder dysfunction**.
- While it causes saddle anesthesia and urinary symptoms, the **asymmetrical motor weakness** (left leg only) and **prominent radicular pain** extending down the leg are more characteristic of cauda equina syndrome.
- Conus lesions typically present with more **symmetric bilateral deficits** rather than the unilateral pattern seen here.
*Anterior spinal cord syndrome*
- Characterized by **bilateral motor paralysis** and **loss of pain and temperature sensation** below the lesion, with **preservation of proprioception and vibratory sensation**.
- It would not typically present with the isolated **saddle anesthesia** and **radicular pain** described in the patient.
*Brown-sequard syndrome*
- Results from a **hemicord lesion**, causing **ipsilateral motor paralysis** and loss of proprioception/vibration below the lesion, and **contralateral loss of pain and temperature sensation**.
- The patient's symptoms of **bilateral saddle anesthesia** and **bowel/bladder dysfunction** do not align with the characteristic unilateral sensory and motor presentation of Brown-Sequard syndrome.
Parasympathetic sacral outflow US Medical PG Question 5: A 45-year-old male is brought to the emergency department by emergency medical services after sustaining a gunshot wound to the abdomen. He is unresponsive. His temperature is 99.0°F (37.2°C), blood pressure is 95/58 mmHg, pulse is 115/min, and respirations are 20/min. Physical examination reveals an entry wound in the left abdominal quadrant just inferior to the left lateral costal border. Abdominal CT shows the bullet trajectory through the left abdominal cavity. Which of the following structures has the bullet most likely penetrated?
- A. Transverse colon
- B. Ascending colon
- C. Descending colon (Correct Answer)
- D. Sigmoid colon
- E. Superior duodenum
Parasympathetic sacral outflow Explanation: ***Descending colon***
- The **descending colon** is located in the left abdominal cavity, specifically in the left upper quadrant and extending into the left lower quadrant, making it highly susceptible to injury from a gunshot wound in the **left abdominal quadrant** just inferior to the left lateral costal border.
- Its position aligns directly with the described entry point and bullet trajectory.
*Transverse colon*
- The **transverse colon** lies more centrally in the upper abdomen, spanning from the right to the left upper quadrants.
- While possible to be hit by a left-sided entry wound, the trajectory described as "inferior to the left lateral costal border" makes the descending colon a more direct and likely target.
*Ascending colon*
- The **ascending colon** is located in the **right abdominal cavity**, specifically in the right upper and lower quadrants.
- A wound inferior to the left lateral costal border would be on the opposite side of the abdomen and thus unlikely to penetrate the ascending colon.
*Sigmoid colon*
- The **sigmoid colon** is located more inferiorly in the **left lower quadrant** and pelvis.
- While on the left side, the entry wound described as "inferior to the left lateral costal border" is generally higher than the typical location of the sigmoid colon.
*Superior duodenum*
- The **superior duodenum** is located in the **right upper quadrant** of the abdomen, anterior to the head of the pancreas.
- Its position on the right side makes it highly unlikely to be penetrated by a gunshot wound to the left abdominal quadrant.
Parasympathetic sacral outflow US Medical PG Question 6: A 48-year-old man with retroperitoneal sarcoma requires extensive resection including portions of the sympathetic chain from T10-L2 and the celiac/superior mesenteric ganglia. Preoperative evaluation is needed to predict postoperative autonomic consequences. The multidisciplinary team must evaluate which combination of deficits is most likely based on the precise anatomical structures being resected and the potential for compensation.
- A. Pan-sympathetic failure including cardiovascular collapse due to loss of all preganglionic outflow
- B. Minimal deficits due to complete bilateral compensation from contralateral sympathetic chain
- C. Complete loss of lower extremity sweating and thermoregulation with normal GI and genitourinary function due to enteric nervous system compensation
- D. Severe orthostatic hypotension, GI dysmotility, and ejaculatory dysfunction with preserved upper body sympathetic function (Correct Answer)
- E. Isolated loss of visceral pain sensation with completely preserved motor and secretory autonomic functions
Parasympathetic sacral outflow Explanation: ***Severe orthostatic hypotension, GI dysmotility, and ejaculatory dysfunction with preserved upper body sympathetic function***
- Resection of the **celiac and superior mesenteric ganglia** and the **sympathetic chain (T10-L2)** drastically reduces total peripheral resistance and venous return regulation, leading to **severe orthostatic hypotension**.
- Disrupting the **lumbar sympathetic chain (L1-L2)** interrupts the pathways for **emission**, while ganglionic resection causes **GI dysmotility** via loss of inhibitory sympathetic input.
*Complete loss of lower extremity sweating and thermoregulation with normal GI and genitourinary function due to enteric nervous system compensation*
- While **anhidrosis** occurs, the **enteric nervous system** cannot fully compensate for the loss of extrinsic sympathetic modulation, leading to significant GI dysfunction.
- Genitourinary function is significantly impacted as the **sympathetic input** required for the contraction of the internal urethral sphincter and seminal vesicles is removed.
*Isolated loss of visceral pain sensation with completely preserved motor and secretory autonomic functions*
- Although **visceral afferents** are interrupted, the resection of **preganglionic and postganglionic motor fibers** guarantees motor and secretory deficits.
- Sympathetic fibers are essential for the **vasoconstriction** and inhibitory signaling to the gut, which cannot remain "completely preserved" after such extensive resection.
*Pan-sympathetic failure including cardiovascular collapse due to loss of all preganglionic outflow*
- **Pan-sympathetic failure** is avoided because segments above **T10** (supplying the head, neck, and upper extremities) and the **adrenal medulla** (if T10-L2 is the primary resection) provide partial function.
- Cardiovascular collapse is unlikely because the **cardiac sympathetic nerves (T1-T4)** remain intact, maintaining heart rate and contractility.
*Minimal deficits due to complete bilateral compensation from contralateral sympathetic chain*
- Sympathetic innervation of the viscera is **bilateral**, but the **celiac and superior mesenteric ganglia** are midline structures; their resection leaves no contralateral alternative.
- Extensive **bilateral resection** of the chain segments at this level ensures profound deficits that cannot be compensated for by remaining neural pathways.
Parasympathetic sacral outflow US Medical PG Question 7: A 62-year-old man with atrial fibrillation undergoes catheter ablation of the pulmonary vein ostia. Post-procedure, he develops gastroparesis, but his cardiologist notes preserved heart rate variability and normal baroreceptor responses. Surgical anatomy review suggests the ablation may have damaged autonomic structures. Evaluate the most likely anatomical explanation for isolated gastric dysmotility with preserved cardiovascular autonomic function.
- A. Injury to the celiac ganglion via retrograde thermal conduction
- B. Direct damage to the enteric nervous system myenteric plexus
- C. Thermal injury to epicardial vagal branches specifically innervating the stomach via the gastric plexus (Correct Answer)
- D. Damage to the stellate ganglion causing isolated sympathetic denervation of the stomach
- E. Disruption of the entire vagal trunk causing pan-autonomic dysfunction
Parasympathetic sacral outflow Explanation: ***Thermal injury to epicardial vagal branches specifically innervating the stomach via the gastric plexus***
- The **vagus nerves** descend behind the heart and form the **esophageal plexus** near the **posterior wall of the left atrium**, making them vulnerable to energy during **pulmonary vein ablation**.
- Damage at this level can disrupt parasympathetic supply to the stomach, causing **gastroparesis**, while sparing the cardiac branches that already branched off superiorly, thereby preserving **heart rate variability**.
*Damage to the stellate ganglion causing isolated sympathetic denervation of the stomach*
- The **stellate ganglion** is located at the **C7-T1** level and supplies sympathetic fibers to the head, neck, and upper limbs; it is anatomically distant from the left atrium ablation site.
- Injury to this ganglion would present with **Horner Syndrome**, not isolated gastric dysmotility.
*Disruption of the entire vagal trunk causing pan-autonomic dysfunction*
- Complete **vagal trunk** damage would result in systemic symptoms, including significant changes in **heart rate variability** and loss of **baroreceptor reflex** sensitivity.
- The preservation of cardiovascular autonomic function indicates that the injury was localized and **distal to the cardiac branches**.
*Injury to the celiac ganglion via retrograde thermal conduction*
- The **celiac ganglion** is located in the **upper abdomen** around the root of the celiac trunk, making it an unlikely target for direct or retrograde thermal injury from the heart.
- This ganglion primarily handles **sympathetic output**; its injury would not typically cause the delayed gastric emptying characteristic of **vagal (parasympathetic) denervation**.
*Direct damage to the enteric nervous system myenteric plexus*
- The **myenteric (Auerbach’s) plexus** is located within the muscular layers of the **stomach wall**.
- Catheter ablation occurs in the **thoracic cavity** at the pulmonary veins; it cannot directly reach or damage the intrinsic nerves located within the abdominal viscus.
Parasympathetic sacral outflow US Medical PG Question 8: A 35-year-old woman with familial dysautonomia (Riley-Day syndrome) presents with absent corneal reflexes, impaired lacrimation, and absent fungiform papillae on the tongue, but preserved parotid gland function. Genetic testing confirms IKBKAP gene mutation affecting neural crest cell migration. Evaluate which embryological principle explains this specific pattern of autonomic and sensory deficits while certain parasympathetic functions remain intact.
- A. Preferential loss of sympathetic neurons with compensatory parasympathetic hyperfunction
- B. Uniform degeneration of both sympathetic and parasympathetic systems proportionally
- C. Selective degeneration of all parasympathetic ganglia with preserved sympathetic function
- D. Failed migration of neural crest cells destined for cranial sensory and parasympathetic ganglia, with preserved placode-derived neurons (Correct Answer)
- E. Isolated defect in myelination of all autonomic preganglionic fibers
Parasympathetic sacral outflow Explanation: ***Failed migration of neural crest cells destined for cranial sensory and parasympathetic ganglia, with preserved placode-derived neurons***
- **Riley-Day syndrome** (IKBKAP mutation) results in the failed development of **neural crest-derived** structures, specifically sensory and autonomic neurons, which explains the **absent corneal reflex** and **fungiform papillae**.
- Certain craniofacial neurons and glandular functions may be spared if they arise from **ectodermal placodes** rather than the neural crest, explaining the complex pattern of deficits.
*Selective degeneration of all parasympathetic ganglia with preserved sympathetic function*
- This syndrome actually involves significant **sympathetic denervation**, leading to signs like postural hypotension and **instability of blood pressure**.
- The deficits are not limited to the parasympathetic system; they involve a widespread loss of **small-fiber sensory** and sympathetic neurons.
*Isolated defect in myelination of all autonomic preganglionic fibers*
- The primary pathology in familial dysautonomia is **neuronal cell death** and failed migration, not primarily a **demyelinating** process.
- Prefibrillar or preganglionic fiber loss occurs, but the most characteristic finding is the **reduced number** of neurons in the **dorsal root** and autonomic ganglia.
*Preferential loss of sympathetic neurons with compensatory parasympathetic hyperfunction*
- While sympathetic loss is prominent, there is no **parasympathetic hyperfunction**; instead, there is impaired **lacrimation** and other parasympathetic deficits.
- Defective **sweating** and gastrointestinal dysmotility reflect a combined failure of both autonomic limbs rather than a compensatory mechanism.
*Uniform degeneration of both sympathetic and parasympathetic systems proportionally*
- The degeneration is not uniform; different populations of **neural crest-derived cells** show varying levels of sensitivity to the **IKBKAP protein** deficiency.
- Features like the **preservation of parotid gland function** (CN IX innervation) highlight that specific autonomic pathways are more resilient than others like the lacrimal pathway.
Parasympathetic sacral outflow US Medical PG Question 9: A 50-year-old man undergoes bilateral truncal vagotomy for refractory peptic ulcer disease. Postoperatively, he develops gastroparesis, but surprisingly maintains normal pancreatic enzyme secretion and normal bile flow during meals. Analysis of his preserved functions suggests alternate autonomic pathways are compensating. Which anatomical principle best explains the preservation of these exocrine functions despite vagotomy?
- A. The pancreas and biliary system receive redundant parasympathetic innervation from pelvic splanchnic nerves
- B. Sympathetic innervation alone is sufficient to maintain basal pancreatic and biliary secretion
- C. Enteric nervous system provides autonomous control independent of vagal input
- D. Parasympathetic innervation to pancreas and gallbladder travels via splanchnic nerves below the vagotomy level
- E. Hormonal regulation via secretin and CCK can maintain function independent of neural control (Correct Answer)
Parasympathetic sacral outflow Explanation: ***Hormonal regulation via secretin and CCK can maintain function independent of neural control***
- The intestinal phase of digestion is primarily mediated by **Secretin** and **Cholecystokinin (CCK)**, which stimulate pancreatic secretion and gallbladder contraction regardless of vagal status.
- These hormonal pathways act as a safeguard, ensuring that **pancreatic enzymes** and **bile flow** continue to meet digestive demands even after a **truncal vagotomy**.
*The pancreas and biliary system receive redundant parasympathetic innervation from pelvic splanchnic nerves*
- **Pelvic splanchnic nerves** (S2-S4) provide parasympathetic innervation only to the **hindgut** (distal third of the transverse colon to the rectum).
- They do not extend superiorly enough to provide autonomic control to the **pancreas** or **biliary system**, which are derivatives of the foregut.
*Sympathetic innervation alone is sufficient to maintain basal pancreatic and biliary secretion*
- **Sympathetic fibers** originating from the **celiac ganglion** generally inhibit gastrointestinal secretions and promote vasoconstriction.
- They cannot substitute for the excitatory **pro-secretory** effects of the parasympathetic system (vagus nerve).
*Enteric nervous system provides autonomous control independent of vagal input*
- While the **enteric nervous system (ENS)** can coordinate local peristalsis and mucosal secretion, it lacks the broad integrative capacity to fully stimulate large-scale **exocrine glands** like the pancreas without extrinsic input.
- The ENS works in tandem with the vagus, but it cannot completely replicate the **vago-vagal reflex** necessary for the cephalic and gastric phases of secretion.
*Parasympathetic innervation to pancreas and gallbladder travels via splanchnic nerves below the vagotomy level*
- **Splanchnic nerves** typically refer to the **greater, lesser, and least splanchnic nerves**, which carry **sympathetic** preganglionic fibers, not parasympathetic ones.
- There are no known significant anatomical pathways where **parasympathetic fibers** bypass the truncal vagus to reach the hepatobiliary tree via inferior spinal levels.
Parasympathetic sacral outflow US Medical PG Question 10: A 42-year-old man with chronic pancreatitis undergoes celiac plexus block for pain management. Post-procedure, he experiences orthostatic hypotension and diarrhea but maintains normal heart rate responses to Valsalva maneuver and normal pupillary reflexes. Analysis of these findings suggests selective blockade of specific autonomic pathways. Which combination of autonomic effects best explains this clinical presentation?
- A. Blockade of sympathetic outflow to splanchnic vessels with preserved cardiac and cranial parasympathetic function (Correct Answer)
- B. Complete parasympathetic denervation with intact sympathetic function to all organs
- C. Combined sympathetic and parasympathetic blockade to abdominal viscera only
- D. Selective parasympathetic blockade to the GI tract with preserved sympathetic tone
- E. Disruption of both afferent and efferent pathways of all autonomic reflexes
Parasympathetic sacral outflow Explanation: ***Blockade of sympathetic outflow to splanchnic vessels with preserved cardiac and cranial parasympathetic function***
- Celiac plexus block inhibits the **splanchnic nerves**, causing **vasodilation** and venous pooling in the abdominal viscera, which leads to **orthostatic hypotension**.
- The **diarrhea** results from **unopposed vagal activity** in the gastrointestinal tract because sympathetic inhibitory signals are blocked while the vagus nerve remains unaffected.
*Complete parasympathetic denervation with intact sympathetic function to all organs*
- Parasympathetic denervation would typically cause **constipation** and **tachycardia**, which contradicts this patient's presentation of diarrhea.
- Normality of the **pupillary reflex** and **Valsalva maneuver** confirms that cranial and cardiac parasympathetic pathways are fully intact.
*Combined sympathetic and parasympathetic blockade to abdominal viscera only*
- A combined block would neutralize both systems in the gut, likely resulting in **decreased motility** or ileus rather than secretory diarrhea.
- Diarrhea specifically identifies that the **parasympathetic (vagal) innervation** is functioning without the normal counter-regulatory sympathetic tone.
*Selective parasympathetic blockade to the GI tract with preserved sympathetic tone*
- Loss of parasympathetic tone would lead to **decreased peristalsis** and would not explain the occurrence of **orthostatic hypotension**.
- Preserved sympathetic tone would maintain **vasoconstriction**, preventing the blood pressure drop observed upon standing.
*Disruption of both afferent and efferent pathways of all autonomic reflexes*
- This would result in a total loss of the **Valsalva heart rate response** and **pupillary light reflexes**, both of which were documented as normal.
- Such a global disruption is inconsistent with a localized procedure like a **celiac plexus block**, which targets specific abdominal pathways.
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