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The Nervus Intermedius: A Review of Its Anatomy, Function, Pathology, and Role in Neurosurgery R. Shane Tubbs1, Dominik T. Steck1, Martin M. Mortazavi1, Aaron A. Cohen-Gadol2 Key words Ⅲ BACKGROUND: Geniculate neuralgia, although uncommon, can be a debili- Ⅲ Anterior inferior cerebellar tating pathology. Unfortunately, a thorough review of this pain syndrome and the Ⅲ Cranial Ⅲ clinical anatomy, function, and pathology of its most commonly associated nerve, Ⅲ the nervus intermedius, is lacking in the literature. Therefore, the present study Ⅲ Microvascular decompression aimed to further elucidate the diagnosis of this pain syndrome and its surgical Ⅲ Neuralgia treatment based on a review of the literature. Ⅲ Nervus intermedius Ⅲ Ⅲ METHODS: Using standard search engines, the literature was evaluated for Ⅲ Wrisberg nerve germane reports regarding the nervus intermedius and associated pathology. A summary of this body of literature is presented. Abbreviation and Acronym MRI: Magnetic resonance imaging Ⅲ RESULTS: Since 1968, only approximately 50 peer-reviewed reports have been published regarding the nervus intermedius. Most of these are single-case From 1Pediatric Neurosurgery, Children’s Hospital, Birmingham, Alabama; and reports and in reference to geniculate neuralgia. No report was a review of the 2Goodman Campbell and Spine, Department of literature. Neurological Surgery, Indiana University, Indianapolis, Indiana, USA Ⅲ CONCLUSIONS: Neuralgia involving the nervus intermedius is uncommon, but To whom correspondence should be addressed: when present, can be life altering. Microvascular decompression may be Aaron A. Cohen-Gadol, M.D., M.Sc. effective as a treatment. Along its cisternal course, the nerve may be difficult to [E-mail: [email protected]] distinguish from the facial nerve. Based on case reports and small series, Citation: World Neurosurg. (2013) 79, 5/6:763-767. http://dx.doi.org/10.1016/j.wneu.2012.03.023 long-term pain control can be seen after nerve sectioning or microvascular Journal homepage: www.WORLDNEUROSURGERY.org decompression, but no prospective studies exist. Such studies are now neces- Available online: www.sciencedirect.com sary to shed light on the efficacy of surgical treatment of nervus intermedius 1878-8750/$ - see front matter © 2013 Elsevier Inc. neuralgia. All rights reserved.

INTRODUCTION ANATOMY AND FUNCTIONS which is often crescent shaped, of the ner- The nervus intermedius was first identified The nervus intermedius consists of fibers vus intermedius to the vestibulocochlear in 1563, and it was Heinrich August Wris- derived from the superior salivary nucleus nerve has been found to be approximately 8 berg who named it the “portio media inter whose stimulation results in secretion of mm (11, 20). Inside the meatus, the motor comunicantem faciei et nervum auditorium” in the lacrimal and submandibular and sub- root of the facial nerve and the nervus inter- 1777 (1). This nerve (Figure 1), often re- lingual glands (4). Traveling along this medius are usually bound together as a sin- ferred to as the Wrisberg nerve, carries nerve are sensory fibers derived from the gle structure. parasympathetic fibers to the lacrimal and gustatory receptors destined for the supe- In the , the facial nerve nasopalatine glands and transmits sensory rior pole of the in the me- continues its course through the facial ca- information from the and various dulla and fibers for cutaneous sensation of nal. The nerve is supplied from branches of skin areas of the nose and concha of the parts of the destined for the dorsal part the middle meningeal, maxillary, and pos- ear (8, 20, 22, 28). A cutaneous branch of the trigeminal tract (31). The course of terior auricular . Between the co- arises near the origin of the chorda tym- the nervus intermedius and the motor root chlea and the , it runs pani nerve and joins with the auricular of the facial nerve can be divided into cister- laterally above the vestibule. Reaching the branch of the to supply the nal, meatal, labyrinthal, and extracranial medial wall of the epitympanic recess, the external auditory canal and concha of the parts. Rhoton et al. (20) found that, on av- geniculum (external genu) is formed. This external ear. It is this innervation that al- erage, the length of all 3 segments was 22 point, above the base of the , is the lows herpetic vesicles to be identified in mm. The nerve takes its name from its in- location of the (14). the ear with viral infection of the genicu- termediate position between the facial and Here the nerve gives rise to the greater late ganglion, the so-called Ramsay-Hunt superior portion of the vestibular petrosal nerve (greater superficial petrosal syndrome (20). (20). The average length of adherence, nerve), which carries parasympathetic fi-

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Section of the nervus intermedius may two of them for more than 10 years. The decrease the cutaneous sensitivity in the first patient, a 43-year-old woman, suf- area around the concha of the external ear, fered from attacks of right-sided and sensation from anterior nasopharynx and pain for 7 years that later became tympanic membrane, part of the external associated with severe pain in the right auditory canal, and the area behind the ear

PAIN ear. During surgery and under local anes- and over the mastoid process (11, 22). Stim- thesia, the facial, vestibulocochlear, and ulation of the nervus intermedius can cause glossopharyngeal nerves, including the referred pain to the ear, and the projection nervus intermedius, were explored; stim- of fibers from this nerve might also explain ulation of the nervus intermedius resulted referred pain to the face after irritation of in pain in the ear and right face. The same the nervus intermedius (20). Therefore, the symptoms could be produced when stim- Figure 1. Cadaveric dissection of the right nervus intermedius plays an important role ulating the vestibulocochlear nerve. The porus acousticus noting the facial, nervus in the surgical treatment of neuralgia of the facial (inadvertently) and vestibuloco- intermedius, and vestibulocochlear nerves. external auditory canal (see later) (20). In- chlear nerves and the nervus intermedius terestingly, Ashram et al. (6) described elec- were sectioned. No recurrence was noted tromyography activity in the orbicularis oris at 15 years of follow up. The second pa- bers supplying the lacrimal, nasal, and pal- muscle after stimulation of the nervus inter- tient, a 56-year-old man with attacks of atine glands (22, 29). The tympanic cavity medius. left-sided facial pain that were associated and the nerve are separated only by a thin Burmeister et al. (8) conducted a study in with ipsilateral lacrimation and nasal layer of bone and this layer might be absent, which they tried to identify the nervus inter- congestion, underwent left greater petro- so in some individuals, there is only the mu- medius with 3-T magnetic resonance imag- sal neurectomy, which brought relief for 3 cosa between the nerve and the cavity of the ing (MRI). Their conclusion was that the years. A third patient, a 65-year-old man middle ear, and therefore the nerve might nervus intermedius can be depicted reliably who suffered from attacks of pain on the be easily affected by infections of the middle with MRI, which might be helpful, espe- left side of the face without lacrimation, ear. Possible anomalies include the nerve cially in the diagnosis of the source of tu- nasal congestion, or ear pain, also under- lying in the wall of the with mors in this region. went sectioning of the nervus interme- the nerve emerging from the mastoid pro- dius. Lacrimation was lost, but no loss of cess and division of the nerve within the occurred, and the patient became (branches leave the temporal GENICULATE NEURALGIA AND ITS pain-free postoperatively. The fourth pa- bone through different foramina in this SURGICAL TREATMENT tient, a 36-year-old man, complained of case). An anterolateral turn toward the pa- Although nervus intermedius (geniculate) daily headaches for 6 to 8 weeks per year. rotid gland describes the extracranial neuralgia is rare and difficult to diagnose, a The pain was in the right , eye, fore- course of the facial nerve after it emerges number of different surgical treatment op- head, temple, and behind the right ear. In from the (14, 31). tions have evolved, leading to more confu- this case, a large internal auditory artery Rhoton et al. (20) and Oh et al. (16) found sion about the most appropriate approach. was seen between the facial and vestibu- up to 4 to 5 roots that made up the nervus The International Headache Society (10) de- locochlear nerves. Sectioning of the ner- intermedius, although a single root was the fines nervus intermedius neuralgia as inter- vus intermedius caused decrease of lacri- most common. Additionally, Rhoton et al. mittent episodes of pain located deep in the mation and loss of taste on the anterior (20) stated that in approximately 20% of ear that last for seconds or minutes; the two-thirds of the tongue and immediate cases, it is impossible to identify the nervus posterior wall of the auditory canal may be a relief of pain (24). There is some variation intermedius along its intracisternal course trigger zone. The pain can be accompanied in the distribution of pain among the because it is intimately attached to the ves- by disorders of lacrimation, salivation, and above patients (some suffering from fa- tibular part of the vestibulocochlear nerve taste (10). In 1909, Clark and Taylor (9) were cial pain) making it difficult to assess who and does not separate from it until the inter- the first to report success in treating facial reliably harbored geniculate neuralgia. nal acoustic meatus. pain with resection of the geniculate gan- Lovely and Janetta (13) reported 14 cases Preganglionic fibers from the superior glion. Of note, some have advocated tran- of patients with the primary complaint of salivatory nucleus in the travel to the section of the nervus intermedius for deep pain, often in combination in the greater chronic cluster headaches (15, 22). In fact, with atypical facial pain or pain. Vas- petrosal nerve, and the postganglionic fi- Rowed (22) reported a 75% success rate us- cular compression of the trigeminal, glos- bers innervate the as well as ing this technique in such patients. Paren- sopharyngeal, or vagus nerve or the nervus the glands of the nose and . Pregan- thetically, this investigator found that hear- intermedius was observed in almost every glionic parasympathetic fibers from the ing impairment was the most frequent case and was assumed to be a cause of the pons travel to the serious complication after sectioning of the primary or secondary complaints in these in the and innervate the nervus intermedius (22). patients (Figures 2 and 3A). submandibular, the sublingual, and the ac- Sachs (24) followed up four patients These cases emphasize the importance cessory salivary glands. after section of the nervus intermedius, of the nervus intermedius in otalgia. Four

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Rupa et al. (23) reported 14 patients with sented with both trigeminal and nervus geniculate neuralgia who underwent nervus intermedius neuralgia (touching the nose intermedius sectioning. This cohort was in- and the external auditory meatus caused cluded among 18 cases of primary otalgia pain in the second/third divisions of the with additional procedures, including and ear, respectively). resection of the geniculate ganglion, During surgery, the anterior inferior cer- glossopharyngeal, vagus, tympanic, and ebellar artery was found adherent to the chorda tympani nerves. Among all pa- facial and vestibulocochlear nerves and tients, pain relief was achieved in 72.2% the root of the trigeminal nerve was com- PAIN (23). Reported side effects of nervus in- pressed by three large and a branch termedius sectioning included decreased of the superior cerebellar artery. After de- lacrimation, salivation, and taste (23). compressing the nerves from the vessels Figure 2. Schematic drawing of the surgical Pulec (18) has also reported good results and rhizotomy of the sensory root of the approach to the nervus intermedius for after nervus intermedius sectioning for trigeminal nerve, the patient became pain microvascular decompression or sectioning. geniculate neuralgia. free (7). Saers et al. (25), Younes et al. Sakas et al. (26) reported a case of a 52- (30), and Özer et al. (17) reported similar patients had to undergo multiple proce- year-old woman with episodes of pain of cases of suspected nervus intermedius dures, and in two of them, lasting relief was the right auditory canal, pinna and retro- neuralgia in which the anterior inferior not obtained before the nervus intermedius mastoid area, as well as right-sided tinni- cerebellar artery compressed the nervus was sectioned. The sectioning of the nervus tus, loss, imbalance, and . intermedius and mobilization of the ar- intermedius was well tolerated in all pa- Neuroimaging demonstrated a tortuous an- tery cured the pain. Such neurovascular tients, and no neurologic deficits or altera- terior inferior cerebellar artery compress- compression led to demyelination at the tions in taste or lacrimation were reported ing the facial and vestibulocochlear nerves root entry zone (25). Interestingly, some (13). The efficacy of pain relief through mi- at the . During sur- have questioned vascular compression as crovascular decompression or sectioning of gery, the artery was mobilized and sepa- a cause of geniculate neuralgia (5). the nervus intermedius cannot be reliably rated from the nerves. All symptoms, Alfieri et al. (2) found that the mean dis- established by this study. Some patients including pain, , vertigo, and tance laterally from the brain stem of cen- suffered from atypical face pain as well, and hearing loss, improved during the follow- tral myelin for the nervus intermedius was therefore, a heterogeneous group of pa- ing months (26). Belloti et al. (7) dis- 0.5 mm on the medial side of the nerve and tients was analyzed. cussed a 65-year-old patient who pre- 0.33 on its lateral side. The Obersteiner- Redlich zone or glial-Schwann cell junction for the medial and lateral sides of the nerve was 0.279 mm and 0.33 mm, respectively (2). With these data, it appears that the ner- vus intermedius is closer to the brain stem compared with other (2). Riederer et al. (19) described an inter- esting case of familial geniculate neural- gia and concluded that an X-linked domi- nant inheritance was most likely the cause of the occurrence of nervus intermedius neuralgia in the family. In some cases, a genetic susceptibility for cranial neural- gias might be present (32), and one theory suggested a mutation of the Nav 1.7 so- dium channel with resultant nerve hyper- excitability (3).

PERSPECTIVES ON SURGICAL TREATMENT OF GENICULATE NEURALGIA The previously discussed studies regard- ing the surgical treatment of geniculate Figure 3. Intraoperative images of the surgical approach (A) to the nervus intermedius in a patient neuralgia suffer from similar limitations. with geniculate neuralgia. Note the surrounding nerves (B). An offending vessel was identified and The studied patients suffered from heter- pulled away (C) from the nerve and held in place with a Teflon implant (D). ogeneous pain syndromes that included

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poorly described face pain. The number are now necessary to shed light on the effi- ate nerve and manifesting as hemifacial spasm. Case of patients mentioned in the individual cacy of surgical treatment of nervus inter- report. J Neurosurg 84:277-279, 1996. studies and the follow-up durations are medius neuralgia. A thorough knowledge 13. Lovely TJ, Jannetta PJ: Surgical management of also limited. of the anatomy of this nerve is necessary geniculate neuralgia. Am J Otol 18:512-517, 1997. The efficacy of exploratory surgery with when treating patients presenting with transection of nervus intermedius for long- symptoms due to pathology along its 14. Monkhouse WS: The anatomy of the facial nerve. PAIN Ear Nose Throat J 69:677-683, 686-687, 1990. term relief of geniculate neuralgia remains course. unconvincing. Therefore, patient selection 15. Morgenlander JC, Wilkins RH: Surgical treatment of remains especially important, and the risk cluster headache. J Neurosurg 72:866-871, 1990. of vestibulocochlear nerve dysfunction and 16. Oh CS, Chung IH, Lee KS, Tanaka S: Morphological resultant persistent dizziness and balance REFERENCES study on the rootlets comprising the root of the inter- dysfunction should be carefully considered mediate nerve. Anat Sci Int 78:111-113, 2003. 1. Alfieri A, Strauss C, Prell J, Peschke E: History of the during manipulation of the VII/VIII com- nervus intermedius of Wrisberg. Ann Anat 192:139- 17. Özer FD, Duransoy YK, Camlar M: Atypic geniculate plex. Glossopharyngeal neuralgia with a 144, 2010. neuralgia: atypic anatomic correlation of cranial primarily otitic component may mimic nerve roots and AICA. Acta Neurochir (Wien) 151: 2. Alfieri A, Fleischhammer J, Strauss C, Peschke E: 1003-1004; discussion 1004, 2009. geniculate neuralgia; this overlap in presen- The central myelin-peripheral myelin transitional tation should be considered during explora- zone of the nervus intermedius and its implications 18. Pulec JL: Geniculate neuralgia: long-term results of tion of the posterior fossa cranial nerves for microsurgery in the . Clin surgical treatment. Ear Nose Throat J 81:30-33, because the glossopharyngeal nerve may be Anat 2011 Dec 20. [Epub ahead of print] 2002. involved in vascular compression. 3. Alfieri A, Strauss C: Familial occipital neuralgia with 19. Riederer F, Sédor PS, Linnebank M, Ettlin DA: Fa- sporadic nervus intermedius neuralgia (NIN). J milial occipital and nervus intermedius neuralgia in Headache Pain 12:657, 2011. a Swiss family. J Headache Pain 11:335-338, 2010.

TUMORS INVOLVING THE 4. Alfieri A, Fleischhammer J, Prell J: The functions of 20. Rhoton AL Jr, Kobayashi S, Hollinshead WH: Ner- NERVUS INTERMEDIUS the nervus intermedius. AJNR Am J Neuroradiol 32: vus intermedius. J Neurosurg 29:609-618, 1968. E144; author reply E145, 2011. Scheller et al. (27) reported a possible case 21. Rizer FM, Guthikonda M, Lippy WH, Schuring AG: of case of nervus intermedius schwannoma 5. Alfieri A, Strauss C: Microvascular decompression Simultaneous presentation of facial nerve neuroma and otosclerosis. Am J Otol 15:427-430, 1994. that presented with progressive left-sided may be an effective treatment for nervus interme- dius neuralgia. J Laryngol Otol 125:765; author reply hearing loss and dizziness. Rizer et al. (21) 765, 2011. 22. Rowed DW: Chronic cluster headache managed by reported a 38-year-old man with left-sided nervus intermedius section. Headache 30:401-406, hearing loss and tinnitus. MRI demon- 6. Ashram YA, Jackler RK, Pitts LH, Yingling CD: In- 1990. strated a lesion in the lateral end of the left traoperative electrophysiologic identification of the nervus intermedius. Otol Neurotol 26:274-279, 23. Rupa V, Saunders RL, Weider DJ: Geniculate neural- internal auditory canal. During surgery, a 2005. gia: the surgical management of primary otalgia. J tumor was found that attached only to part Neurosurg 75:505-511, 1991. 7. Bellotti C, Medina M, Oliveri G, Ettorre F, Barrale of the facial nerve and was removed with 24. Sachs E Jr: The role of the nervus intermedius in nervus intermedius sectioning. Kudo et al. S, Sturiale C, Melcarne A: Neuralgia of the inter- mediate nerve combined with trigeminal neural- facial neuralgia. Report of four cases with observa- (12) reported a patient who presented with gia: case report. Acta Neurochir (Wien) 91:142- tions on the pathways for taste, lacrimation, and left hemifacial spasm. A small mass (later 143, 1988. pain in the face. J Neurosurg 28:54-60, 1968. found to be a schwannoma) arising from 25. Saers SJ, Han KS, de Ru JA: Microvascular decom- 8. Burmeister HP, Baltzer PA, Dietzel M, Krumbein I, the nervus intermedius, adhering to and pression may be an effective treatment for nervus Bitter T, Schrott-Fischer A, Guntinas-Lichius O, intermedius neuralgia. J Laryngol Otol 12:1-3, 2011 compressing the facial nerve, was found. Kaiser WA: Identification of the nervus intermedius [Epub ahead of print] The nervus intermedius was sectioned and using 3T MR imaging. AJNR Am J Neuroradiol 32: 460-464, 2011. the patient was free of spasms after surgery 26. Sakas DE, Panourias IG, Stranjalis G, Stefanatou and at long-term follow-up. MP, Maratheftis N, Bontozoglou N: Paroxysmal 9. Clark LP, Taylor AS: True tic douloureux of the otalgia due to compression of the intermediate sensory filaments of the facial nerve. I. Clinical nerve: a distinct syndrome of neurovascular conflict report of a case in which cure was effected by confirmed by neuroimaging. Case report. J Neuro- physiological extirpation of the geniculate gan- surg 107:1228-1230, 2007. CONCLUSIONS glion. I1. Report of surgical treatment. JAMA 53: 2144-2146, 1909. Neuralgia involving the nervus intermedius 27. Scheller C, Rachinger J, Prell J, Kornhuber M, Strauss C: Schwannoma of the intermediate nerve. J is uncommon, but when present, it can be 10. Headache Classification Committee of the Interna- Neurosurg 109:144-148, 2008. life altering. Microvascular decompression tional Headache Society: Classification and diag- may be effective as a treatment. Along its nostic criteria for headache disorders, cranial neu- 28. Smith JJ, Breathnach CS: Functions of the seventh ralgias and facial pain. Cephalalgia 8(Suppl 7):1-96, cranial nerve. Ear Nose Throat J 69:688-691, 694- cisternal course, the nerve may be difficult 1988. 695, 1990. to distinguish from the facial nerve. Based on case reports and small series, long-term 11. Jordan DR: The nervus intermedius. Arch Ophthal- 29. Thomsen J, Borum P, Tos M, Zilstorff K: Nervus pain control can be seen after nerve section- mol 111:1691-1692, 1993. intermedius in acoustic neuromas: a critical evalua- tion of intermedius nerve testing, with special refer- ing or microvascular decompression, but 12. Kudo A, Suzuki M, Kubo N, Kuroda K, Ogawa A, ence to the nasolacrimal reflex. Am J Otol 3:21-27, no prospective studies exist. Such studies Iwasaki Y: Schwannoma arising from the intermedi- 1981.

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30. Younes WM, Capelle HH, Krauss JK: Microvascular 32. Wang Y, Yu CY, Huang L, Riederer F, Ettlin D: Fa- Received 17 November 2011; accepted 29 March 2012 decompression of the anterior inferior cerebellar milial neuralgia of occipital and intermedius nerves Citation: World Neurosurg. (2013) 79, 5/6:763-767. artery for intermediate nerve neuralgia. Stereotact in a Chinese family. J Headache Pain 12:497-500, http://dx.doi.org/10.1016/j.wneu.2012.03.023 Funct Neurosurg 88:193-195, 2010. 2011. Journal homepage: www.WORLDNEUROSURGERY.org 31. Walker HK: Cranial nerve VII: the facial nerve and Available online: www.sciencedirect.com taste. In: Walker HK, Hall WD, Hurst JW, editors. Conflict of interest statement: The authors declare that the 1878-8750/$ - see front matter © 2013 Elsevier Inc. Clinical Methods: The History, Physical, and Labora- article content was composed in the absence of any All rights reserved. tory Examinations. 3rd edition. Boston: Butterworths, commercial or financial relationships that could be 1990. construed as a potential conflict of interest.

Early versus Delayed Endoscopic Surgery for Carpal Tunnel Syndrome: Prospective Randomized Study PERIPHERAL NERVE P. Sarat Chandra, Pankaj Kumar Singh, Vinay Goyal, Avnish Kumar Chauhan, Nirmal Thakkur, Manjari Tripathi

Key words Ⅲ OBJECTIVE: To compare the effects of early versus delayed endoscopic Ⅲ Carpal tunnel release surgery in patients with moderately severe carpal tunnel syndrome (CTS). Ⅲ Carpal tunnel syndrome Ⅲ Endoscopic surgery Ⅲ METHODS: The study included 100 patients with CTS. Investigations per- Ⅲ Flexor retinaculum formed before surgery excluded secondary causes. Patients with moderately Abbreviations and Acronyms severe CTS (grade 3–4) were randomly assigned. Bland’s neurophysiologic APB: Abductor pollicis brevis grading scale for CTS was used to assess the patients. Patients underwent an CTS: Carpal tunnel syndrome endoscopic carpal tunnel release using an indigenously designed instrument. EP: Electrophysiology ICMR: Indian Council for Medical Research Ⅲ RESULTS: Following a course of conservative treatment, surgical treatment NSAIDs: Nonsteroidal antiinflammatory drugs week after diagnosis) and 1> ;51 ؍ was offered in two groups: early surgery (n .(months after diagnosis 6< ;49 ؍ Department of Neurosurgery, All India Institute delayed surgery as per the usual waiting list (n of Medical Sciences, New Delhi, India Improvement in both groups was significant (P < 0.001). When both groups were To whom correspondence should be addressed: compared, improvement was better for the early surgery group (P < 0.001; Manjari Tripathi, D.M. [E-mail: [email protected]] confidence interval 6.35–9.12). Citation: World Neurosurg. (2013) 79, 5/6:767-772. Ⅲ CONCLUSIONS: On the basis of this study, early endoscopic surgery is http://dx.doi.org/10.1016/j.wneu.2012.08.008 Journal homepage: www.WORLDNEUROSURGERY.org proposed in patients with moderately severe CTS. Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved. of choice is surgical dissection of the trans- ance. Generally, most reviews state that verse carpal ligament (flexor retinaculum) both endoscopic and open techniques are INTRODUCTION with decompression of the nerve (16, 18). safe and equally effective in relieving the Carpal tunnel syndrome (CTS) is the most Open dissection of the transverse carpal symptoms of CTS. common nerve entrapment syndrome oc- ligament has been the standard procedure The timing of surgery (early or delayed) is curring in the upper extremity, with a prev- performed for Ͼ50 years (5, 21). Endo- also important. Most patients who are rou- alence of up to 9% (18). Classic symptoms scopic surgical techniques were developed tinely considered for surgery are usually of CTS include pain, paresthesia (character- and introduced to ameliorate the inconve- given a trial of conservative treatment, fol- istically worse during the night, termed bra- niences and adverse events of open dissec- lowed by surgery after 3–6 months. Earlier chialgia paresthetica nocturna), and hypoesthe- tion. Endoscopic carpal tunnel release was studies have shown that both conservative sia in the . Weakness and atrophy of introduced by Okutsu et al. in 1987 (15). and surgical treatments lead to improved the abductor pollicis brevis (APB) and mus- Subsequently, several other clinicians de- outcomes. However, the improvement has cles innervated by the median nerve may veloped endoscopic techniques for dissec- been shown to be better in patients who also be observed. The characteristic prolon- tion of the transverse carpal ligament (3, underwent surgery (20, 21). gation of distal motor latency confirms the 12-23). These techniques were introduced Treatment for moderately severe (Bland diagnosis (1, 25). Initially, a conservative with the presumed advantage of being min- score 3–4 [defined subsequently]) (25) CTS approach to treatment is preferred for per- imally invasive with decreased surgical du- is controversial. Few studies favored both sisting symptoms; however, the treatment ration, resulting in better patient compli- surgery and conservative treatment. How-

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