兽研引言
手部周围神经损伤在临床实践中较为常见，可由钝性、穿透性或医源性创伤引起。此类损伤的严重程度从神经失用至完全断裂不等，若未得到正确识别和处理，可能导致持续性感觉缺损[1-3]。
手部浅表神经因其解剖位置而易受损伤，但在低能量创伤后神经束经皮肤挤出极为罕见。识别此类结构至关重要，因为误判可能导致处理不当或错失诊断机会。
除解剖学知识外，与病理科的有效沟通对于确保标本得到适当处理也至关重要。我们报告一例罕见的疑似指神经束在猫抓伤后外露的病例，并讨论其临床和诊断意义。
病例报告
一名80岁女性在试图抱起其猫时被猫抓伤后不久到急诊科就诊。其生命体征无异常。
体格检查发现左手背侧、第二掌指关节近端处有一线形、狭窄、约1 cm的裂伤，深度未记录（图1）。伤口处有一3-4 cm的线状结构突出。患者诉其与女儿曾尝试移除该结构，但因疼痛未能成功。
[图：患者到达分诊时的伤口，可见一段明显较长的突出组织。]
轻轻牵拉时，该结构远端似乎固定于皮下，近端游离，但未引起手指活动。神经血管检查显示远端脉搏完好，运动功能保留。然而，食指背侧和内侧出现新的感觉缺损（图2）。
[图：左手感觉缺损图。损伤后感觉减退的分布。紫色阴影伴虚线b]
怀疑突出的结构为断裂的皮肤感觉神经，可能为指背神经的分支。推测机制为猫爪沿神经向近端剥离，随后受到牵拉，在远离皮肤损伤处的近端发生断裂，并部分外露。暴露的结构被剪除，伤口予以冲洗并保守处理。
在获得病例报告的书面同意后，为确认该线状结构为神经束的身份/组成，将该线状结构放入标本杯，按低优先级异物手术标本送检病理科。该标本因优先级低，储存约1周，仅行肉眼检查，描述为纤维性物质，随后计划保留两周后丢弃。然而，一名医学生前往病理实验室询问（在标本被丢弃前恰好介入），在讨论样本和病例后，尝试了冰冻切片。尽管组织已变得非常干燥和受损，此时仍被确认为神经束。修正后的病理报告：“本病例最初仅以‘肉眼检查’方式检查和签发。然而，在与临床团队讨论后，对新鲜/未固定组织完成了冰冻切片分析，结果显示与神经组织小碎片相符的表现，符合神经。”
未咨询手外科专家；该决定是在患者知情同意下做出的。感觉缺损因不伴运动功能障碍，被判定不会导致显著残疾。鉴于伤口小、神经长度较长及患者年龄，决定尝试神经吻合需要更大的伤口/切口，其获益不会超过感染风险增加。已告知患者如出现感染迹象应复诊；患者存在持续性感觉缺损，医疗团队通过识别和鉴别神经组织能够客观解释该缺损。截至本文发表时，患者尚未复诊。
讨论
本病例代表一例罕见且不寻常的周围神经损伤表现，涉及轻微穿透性创伤后神经束外露。指背神经为手指背侧提供感觉支配，位置相对浅表，易受损伤[4,5]。
本病例的损伤机制可能涉及猫爪穿透，随后沿阻力最小的路径（包括神经血管平面）剥离。牵拉力可能导致了部分撕脱和神经外露。患者局限性的感觉缺损支持指背神经分支受累。另一种可能的机制是患者自身牵拉，尽管她表示触摸时疼痛。
据我们所知，低能量猫抓伤后周围指神经束外露此前尚未见文献报道，凸显了本病例不寻常的机制和临床表现。
在轻微创伤、牵拉机制及动物相关损伤的情境中，已有不常见周围神经损伤的报道。指神经损伤可发生于看似微不足道的穿透性创伤之后，而动物咬伤则与比初期表现更深层的结构损伤相关[6,7]。此外，神经组织可能被误认为异物，或在小型操作中被意外遇到，这强调了在不典型表现中解剖学识别的重要性。然而，这些报道均未描述如本病例中所观察到的神经束真正经皮肤外露的情况。
在与病理科沟通后了解到，最初提交的标本缺乏足够的临床细节，导致评估受限。仅在直接澄清之后才获得组织学确认。正确的标本处理，包括置于福尔马林中，本可改善组织保存和诊断质量[8]。此外，标注不具体的标本除非明确要求，否则可能不会接受详细分析。临床医生在提交标本时应提供清晰的临床背景和诊断意图，以确保得到适当的处理。
本分析的局限性包括患者叙述的主观性、对干燥且受损标本使用冰冻切片分析，以及缺乏对患者的随访。这些是急诊室（或在本病例中为分诊区）评估患者时常见的局限性，患者随后离开了。必须指出，该组织为指神经束仅是一种推测；支持这一推测的证据包括损伤位置、感觉分布、原始大体病理评估中对纤维状物质的描述（以推测标本为神经束），以及最终病理报告中与神经相符的发现。
从临床角度来看，本病例强调了在不典型表现中识别解剖结构的重要性。从伤口中露出的线状结构可能被误认为异物、缝线材料或碎屑。未能识别神经组织可能导致处理不当、因试图去除自身组织而造成不适当损伤，或错失适当记录和随访的机会。临床医生在评估不典型伤口发现时应对潜在解剖结构保持高度警惕，因为即使是轻微创伤也可能导致意外的神经损伤。
结论
本病例展示了一例不寻常的周围神经损伤表现，涉及猫抓伤后与神经束相符的周围神经外露。它强调了解剖学识别、全面临床评估和清晰跨学科沟通的重要性。准确的标本标注和适当的保存对于优化诊断结果至关重要。即使是轻微损伤也可能产生具有重要教育价值的意外发现。本病例提醒我们，在临床适当时应准备好适当的知情同意、暂定计划和对标本处理流程的了解。
披露
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作者贡献
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参考文献
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Introduction
Peripheral nerve injuries of the hand are frequently encountered in clinical practice and can result from blunt, penetrating, or iatrogenic trauma. These injuries range in severity from neuropraxia to complete transection and may lead to persistent sensory deficits if not properly identified and managed [1-3].
While superficial nerves of the hand are vulnerable to injury due to their anatomical location, the extrusion of a nerve fascicle through the skin following low-energy trauma is highly unusual. Recognition of such structures is critical, as misidentification may result in improper management or missed diagnostic opportunities.
In addition to anatomical knowledge, effective communication with pathology services is essential to ensure appropriate specimen processing. We present a rare case of a presumed digital nerve fascicle exteriorized following a cat scratch injury and discuss the clinical and diagnostic implications.
Case presentation
An 80-year-old female presented to the emergency department a short time after being scratched by her cat while attempting to pick it up. Her vital signs were unremarkable.
Physical examination revealed a linear, narrow, approximately 1 cm laceration on the dorsal aspect of the left hand, of undocumented depth, just proximal to the second metacarpophalangeal joint (Figure 1). A 3-4 cm threadlike structure was protruding from the wound. The patient reported that she and her daughter had attempted to remove the structure but were unable to do so due to pain.
[图：The patient’s wound upon arrival in triage, with a notably long segment of protruding tissue.]
With gentle traction, the structure appeared tethered distally beneath the skin, with a free proximal end, but it did not result in movement of the digits. Neurovascular examination demonstrated intact distal pulses and preserved motor function. However, a new sensory deficit was noted over the dorsal and medial aspects of the index finger (Figure 2).
[图：Sensory deficit map of the left hand. Distribution of decreased sensation following injury. Purple shading with dashed b]
The protruding structure was suspected to represent a transected cutaneous sensory nerve, likely a branch of the dorsal digital nerve. The presumed mechanism involved the cat claw dissecting along the nerve proximally, followed by tension, transection far proximal to the skin insult, and partial exteriorization. The exposed structure was clipped, and the wound was irrigated and managed conservatively.
After gaining written consent for the case report, and to confirm the identity/composition of the strand as a nerve fascicle, the threadlike structure was placed into a specimen cup and ordered as a surgical specimen, foreign body of low priority to pathology. This specimen, being low priority, was in storage for approximately 1 week, examined only grossly, and described as fibrous material, then was to be retained for two weeks and disposed of afterward. However, the medical student went to the pathology lab to inquire (intervening narrowly before disposal of the specimen), and after discussing the sample and case, a frozen section was attempted. Though the tissue had become very dry and damaged, it was at this point positively identified as a nerve fascicle. The amended pathology report: “This case was originally examined and signed out at a ‘gross examination only.’ However, after discussion with the clinical team, a frozen section analysis was completed on the fresh/unfixed tissue and demonstrates findings consistent with a small fragment of neural tissue compatible with nerve.”
A hand surgery specialist was not consulted; this decision was made with informed consent from the patient. The sensory deficit, being not associated with motor dysfunction, was determined not to cause significant disability. Given the small wound with the significant length of the nerve and the age of the patient, it was decided that attempting nerve anastomosis would require a larger wound/incision and would not have a benefit that outweighed the increased risk of infection. The patient was counseled to return if signs of infection presented themselves; she had a persistent sensory deficit for which the medical team was able to objectively account by identifying and differentiating the nerve tissue. The patient had not followed up as of the publication of this paper.
Discussion
This case represents a rare and unusual presentation of peripheral nerve injury involving exteriorization of a nerve fascicle following minor penetrating trauma. The dorsal digital nerves, which provide sensory innervation to the dorsum of the fingers, are relatively superficial and susceptible to injury [4,5].
The mechanism of injury in this case likely involved penetration by a cat claw followed by dissection along the path of least resistance, including the neurovascular plane. Traction forces may have contributed to partial avulsion and nerve externalization. The patient’s localized sensory deficit supports involvement of a dorsal digital nerve branch. A possible alternative mechanism is traction by the patient herself, though she stated it was painful to the touch.
To our knowledge, exteriorization of a peripheral digital nerve fascicle following a low-energy cat scratch injury has not been previously reported in the literature, highlighting the unusual mechanism and clinical presentation of this case.
Unusual peripheral nerve injuries have been described in the setting of minor trauma, traction mechanisms, and animal-related injuries. Digital nerve injuries may occur following seemingly trivial penetrating trauma, and animal bites have been associated with deeper structural injury than initially apparent [6,7]. Additionally, nerve tissue may be misidentified as foreign material or encountered unexpectedly during minor procedures, emphasizing the importance of anatomical recognition in atypical presentations. However, none of these reports describe true exteriorization of a nerve fascicle through the skin as observed in this case.
In communication with pathology, the initial specimen submission lacked sufficient clinical detail, resulting in limited evaluation. Only after direct clarification was histologic confirmation obtained. Proper specimen handling, including placement in formalin, would have improved tissue preservation and diagnostic quality [8]. Additionally, specimens labeled nonspecifically may not undergo detailed analysis unless explicitly requested. Clinicians should provide clear clinical context and diagnostic intent when submitting specimens to ensure appropriate processing.
The limitations of this analysis include the subjectivity of the story from the patient, the use of frozen section analysis on a dry and damaged specimen, and the lack of follow-up on the patient. These are common limitations in evaluating patients in the emergency room, or in this case, the triage area, after which the patient departed. It must be stated that it is only a presumption that the tissue was a digital nerve fascicle; the evidence to suggest so is the location of the injury, the sensory distribution, the fibrous material description of the original gross pathology evaluation (to presume the specimen to be a fascicle), and the later compatible with nerve finding in the final pathology report.
From a clinical perspective, this case highlights the importance of recognizing anatomical structures in atypical presentations. A threadlike structure emerging from a wound may be misidentified as a foreign body, suture material, or debris. Failure to recognize neural tissue may result in suboptimal management, inappropriate damage from attempting to remove native tissue, or missed opportunities for appropriate documentation and follow-up. Clinicians should maintain a high index of suspicion for underlying anatomical structures when evaluating atypical wound findings, as even minor trauma may result in unexpected nerve injury.
Conclusions
This case illustrates an unusual presentation of peripheral nerve injury involving exteriorization of a peripheral nerve consistent with a nerve fascicle following a cat scratch. It emphasizes the importance of anatomical recognition, thorough clinical assessment, and clear interdisciplinary communication. Accurate specimen labeling and appropriate preservation are essential to optimize diagnostic outcomes. Even minor injuries may yield unexpected findings with significant educational value. This case serves as a reminder to be prepared with appropriate consent, a tentative plan, and an understanding of specimen handling protocols when clinically appropriate.
Disclosures
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Author Contributions
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References
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