Clinical Neurology and Neurosurgery 109 (2007) 535–537
Case report
Acute scrotal pain from idiopathic ilioinguinal neuropathy: Diagnosis and treatment with EMG-guided nerve block B.C. ter Meulen a,∗ , E.W. Peters a , A. Wijsmuller b , R.F. Kropman c , A. Mosch a , D.L.J. Tavy a a
Departments of Neurology and Neurophysiology, Haga-Ziekenhuis, Leyweg 275, 2545CH The Hague, The Netherlands b Department of Surgery, Erasmus-MC, Rotterdam, The Netherlands c Department of Urology, Haga-Ziekenhuis, The Hague, The Netherlands Received 21 February 2007; received in revised form 23 March 2007; accepted 24 March 2007
Abstract Ilioinguinal nerve entrapment presents with a clinical triad of pain in the iliac fossa and inguinal region, sensory abnormalities in the cutaneous distribution of the nerve and tenderness on palpation 2–3 cm medial and below the anterior superior iliac spine. The syndrome poses diagnostic difficulties, as genitofemoral nerve entrapment and non-neurological conditions of the lower abdomen may cause similar pain. We report on a patient with acute groin pain radiating towards the scrotum, caused by ilioinguinal nerve entrapment. The clinical diagnosis was strongly suggested by electromyographic examination, using the monopolar needle as a deep stimulating electrode. Subsequent nerve blockade caused complete relief of symptoms. The technique is described. Future applications for treatment of post-surgical pain are discussed. © 2007 Elsevier B.V. All rights reserved. Keywords: Pain; Ilioinguinal nerve; EMG; Nerve block
1. Introduction
2. Case report
Lesions of the ilioinguinal nerve are commonly seen after lower abdominal surgery, such as herniorraphy, appendectomy and Pfannenstiel-incisions [1]. Idiopathic cases are rare [2,3]. Early recognition is important, as infiltrating the site of entrapment with a local anaesthetic might offer dramatic relief of complaints. We report on a patient and describe an EMG-guided technique to aid nerve localization. After determining the approximate site of entrapment, we carried out a successful block of the ilioinguinal nerve. The patient has been free of pain during 4 months of follow-up.
A 35-year-old man in without a clinically significant medical history presented with a 6-week history of right scrotal pain, arising suddenly after strenuous exercise; the patient had been lifting weights in a gym. He experienced lancinating pain in the right groin, which radiated down towards the right scrotal area. He was barely able to walk and preferred lying down with his right hip flexed. The patient rated the intensity of his pain at 8 on a 10-point numerical pain score. There was no relief from non-steroidal anti-inflammatory drugs or opioids. The patient was referred to the outpatient urology department first. On examination he was afebrile. Genital examination revealed normally descended testicles. The testis and epididymis were normal on palpation and there was no swelling or mass. On abdominal examination the bowel sounds were normal, without tenderness, distension or guarding. The right inguinal region was tender and tapping the skin medial to the anterosuperior spine of the iliac bone elicited
Abbreviations: EMG, electromyogram; MRI, magnetic resonance imaging ∗ Corresponding author. E-mail address: b.termeulen@erasmusmc.nl (B.C. ter Meulen). 0303-8467/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.clineuro.2007.03.011
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severe pain in the right scrotal region (positive Tinel sign). Further neurological examination showed hyperesthesia of the right groin. There was no motor weakness in the anatomical area involved. The superficial abdominal and cremaster reflexes were present on both sides. The complete bloodcount, urinalysis and urine culture, were normal, without infection. Scrotal ultrasound scanning revealed no abnormalities. MRI of the lower abdomen and lumbar spine were equally unremarkable. A neurophysiological consultation was obtained with presumptive diagnosis of ilioinguinal nerve entrapment. Needle examination of the right inguinal area was performed with a 27-Gauge, 37 mm, monopolar EMG injection needle (Oxford Instruments, Old Woking, England), connected to a standard electromyograph. The needle was inserted 3 cm inferior and medial to the anterior superior iliac spine. Electrical stimuli of 5 mA, stimulus duration 200 ms, at 1 Hz were administered through the needle tip, while the needle was advanced gently in an inferior and medial direction, until the patient reported paresthesias in the right scrotum and the approximate localization of the ilioinguinal nerve was found. At this site 4 ml of 2% preservative free lidocaine and 80 mg of methylprednisolone (Depo-medrol® ) was injected. Complete resolution of the pain with anesthesia in the ilioinguinal area was noted several minutes after injection. After the anesthesia resolved the patient remained pain-free. During 4 months follow-up, there was no recurrence of the pain.
3. Discussion The ilioinguinal nerve, together with the iliohypogastric nerve, arises from the first and second lumbar nerves, with variable contribution from the 12th thoracic nerve. The ilioinguinal nerve becomes superficial to the transversus abdominis muscle at midpoint between the iliac crest and the 12th rib. The nerve subsequently passes through the internal oblique muscle (Fig. 1) and external oblique muscles to enter the inguinal canal. It courses ventrally and parallel to
Table 1 Causes of ilioinguinal neuropathies Location
Cause
Retroperitoneal
Surgical incisions (e.g. nefrectomy) Retroperitoneal tumors
Lower abdomen
Entrapment in abdominal muscle layers Surgical incisions
Inguinal canal
Herniorrhaphy Endometriosis Lipoma, leiomyoma
Unknown
After childbirth Spontaneousa
Adapted from Stewart [1]. a Spontaneous neuropathy is probably due to entrapment in the abdominal muscle layers.
the spermatic cord after which it exits the canal through the external inguinal ring. It supplies the skin of the upper and medial part of the thigh, the root of the penis and upper part of the scrotum in the male, and the skin covering the mons pubis and labium majus in the female. Symptoms of ilioinguinal neuropathy are: (a) pain in the iliac fossa and inguinal region, radiating into the genitals or medial part of the thigh, worsened by walking and hip extension and relieved by hip flexion; (b) sensory abnormalities, hyperesthesia in particular, in the distribution of the nerve; (c) tendernes on palpation 2–3 cm medial and below the anterior superior iliac spine. The causes of ilioinguinal neuropathy are summarized in Table 1 [1]. Damage during or after abdominal surgery is most common as a cause. Other causes include mass lesions and childbirth. Spontaneous or “idiopathic” neuropathy is probably due to entrapment between the transverse and internal oblique muscles when they contract [3]. The major differential diagnosis is entrapment of the genitofemoral nerve [4]. The most common causes of genitofemoral nerve entrapment are trauma to the abdominal wall or inguinal ligament, retroperitoneal hematoma or abscess, and pregnancy. Genitofemoral neuropathy also presents with
Fig. 1. The left ilioinguinal and iliohypogastric nerves passing through the internal oblique muscle. Genital branch refers to the genital branch of the genitofemoral nerve. The picture is taken from a human cadaver (courtesy of A. Wijsmuller).
B.C. ter Meulen et al. / Clinical Neurology and Neurosurgery 109 (2007) 535–537
groin pain and paresthesias in the medial inguinal area, medial part of the thigh and scrotum or labium. The internal inguinal ring is often tender. As the areas of skin supplied by the ilioinguinal and genitofemoral nerves overlap, a bedside diagnosis of ilioinguinal versus genitofemoral neuropathy is rather difficult. Non-neurological conditions resembling ilioinguinal neuropathy are: hernia, genitourinary infections and hip disease. The EMG-needle, used as a deep stimulating electrode, may assist in the diagnosis of ilioinguinal neuropathy. Given its superficial course close to the anterior iliac spine, we consider the possibility that we stimulated any nerve other than the ilioinguinal nerve unlikely. Electrical stimulation of the nerve, will elicit typical neuropathic pain, radiating towards the scrotum. Subsequent injection with a local anaesthetic offers relief within minutes. If the procedure does not work, the pain might be caused genitofemoral nerve entrapment instead and a paravertebral block of the L1-L2 spinal nerves should be considered [4]. There are some potential risks to this procedure, including transient femoral nerve palsy and incidental colonic perforation. Ultrasound-guided nerve blocks to enable proper visualization of the nerve are currently under investigation in the pediatric population [5]. Non-invase methods for treating ilioinguinal neuropathy include gabapentin [6] and carbamazepine [7]. If a local nerve block or medication fails to alleviate the symptoms, surgical neurolysis may be required [8].
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The technique we describe was succesful in one patient only and needs to be verified in a larger group of patients. As pain after inguinal herniorraphy is common, Poobalan et al. found a rate as high as 54% [9], we currently investigate the use of EMG-guided blocks for these patients. References [1] Stewart J. Focal peripheral neuropathies. New York: Raven Press; 1993. p. 411–8. [2] Knockaert DC, D’Heygere FG, Bobbaers HJ. Ilioinguinal nerve entrapment: a little-known cause of iliac fossa pain. Postgrad Med J 1989;65(767):632–5. [3] Kopell HP, Thompson WA, Postel AH. Entrapment neuropathy of the ilioinguinal nerve. N Engl J Med 1962;266:16–9. [4] Melville K, Schultz EA, Dougherty JM. Ilioinguinal-iliohypogastric nerve entrapment. Ann Emerg Med 1990;19:925–9. [5] Willschke H, Marhofer P, Bosenberg A, et al. Ultrasonography for ilioinguinal/iliohypogastric nerve blocks in children. Br J Anaesth 2005;95:226–30. [6] Benito-Leon J, Picardo A, Garrido A, Cuberes R. Gabapentin therapy for genitofemoral and ilioinguinal neuralgia. J Neurol 2001;248:907–8. [7] Rizzo M. Successful treatment of painful traumatic mononeuropathy with carbamazepine: insights into a possible molecular pain mechanism. J Neurol Sci 2001;152:103–6. [8] Madura JA, Madura 2nd JA, Copper CM, Worth RM. Inguinal neurectomy for inguinal nerve entrapment: an experience with 100 patients. Am J Surg 2005;189(3):283–7. [9] Poobalan AS, Bruce J, Smith WC, King PM, Krukowski ZH, Chambers WA. A review of chronic pain after inguinal herniorrhaphy. Clin J Pain 2003;19(1):48–54.