pain may also occur, for instance, after a partial damage due to constricting ligatures. The under­lying mechanisms of this type of neuropathic pain differ from acute postoperative pain based on tissue damage. Furthermore, if a previous repair was mesh based, an ongoing inammatory response to the inserted mesh (Sect. 41.3.2.1) may result in CPIP by progressive nerve injury [19, 20]. One rabbit study investigating micro­scopic inguinal nerve reactions to insertion of a prosthetic mesh found nerve axonal dilation and mild-to-severe loss of myelinated axons in nerve fascicles [21]. Both mechanisms may be respon­sible for neuropathic CPIP evolving in the long term in patients. On the other hand, due to long­lasting compression, nerves may already have

responding to catecholamines) and upregulated sodium channels [30–34]. By an upregulated expression of these receptors, hyperexcitability of initially normal surrounding nerves may ensue. Furthermore, a hyperexcitable state may result in an ongoing sensitization of the spinal cord dorsal horn neurons by releasing glutamate acting on postsynaptic N-methyl-D-aspartate (NMDA) receptors [30]. Both mechanisms may contribute to ectopic activity of the concerning nerves and consequent spontaneous pain [30, 35]. Since neighbouring, initially uninjured nerves have intact connections to the skin, pain is often expe­rienced at supercial groin areas [36] as also reected by a painful skin pinching test (Sect.

41.4). Why some patients develop deafferenta­tion pain while others do not is still unclear.

Long-lasting inguinal pain may result in cen­tral sensitization that can be extremely difcult to distinguish from other potential sources of pain. Centralized pain is independent of any peripheral drive [37] such as initiated by inguinal nerves and thus is refractory to peripherally directed treat­ments. Prolonged impulse stimulation along unmyelinated C-bre afferents may cause trans­neuronal morphologic changes to peripheral nerves (‘neuronal plasticity’). Peripheral nerve hyperexcitability may subsequently be caused by a lower threshold of nociceptor afferent periph­eral terminals, a phenomenon termed peripheral sensitization [30]. The extensive quantity and ongoing input resulting from peripheral sensiti­zation may lead to hyperexcitability of the spinal cord and morphological changes more proximal in the central nervous system and thus central sensitization [38–41]. Patients with centralized pain should be excluded from remedial, peripher­ally oriented surgery [16, 42].

Mesh-related pain may occur both after open and after laparo-endoscopic inguinal hernia repairs. In Western countries, laparo-endoscopic repairs such as TEP and TAPP are primarily rec­ommended, providing resources and expertise are available [49]. Approximately 15% of CPIP patients demonstrate a mesh-related pain after an open Lichtenstein repair [28]. The number of patients presenting with mesh-related pain is many times lower following laparo-endoscopic repairs [50]. An explanation for this difference is possibly provided by the position of the mesh in the preperitoneal space. This location is likely benecial not only in terms of evoking fewer cases of neuropathic pain [14, 51] but probably also for generating less mesh-related pain. It is thought, however, that the mesh may exert com­parable mechanical effects irrespective of mode of implantation, open or laparo-endoscopic [50].

haemorrhage or uid retention in the bursa [58]. As a consequence, a sterile inammation of the iliopectineal bursa may occur. As previously mentioned, pain following CPIP may lead to an antalgic gait which occasionally leads to iliopec­tineal bursitis. Sometimes an enlarged bursa can be visualized using magnetic resonance imaging (MRI).

The pathogenesis of dysejaculation involves injury to the vas deferens with or without damage to the inguinal nerves [59, 62, 63]. The vas may be compressed by the mesh or may be injured as a consequence of scar tissue. During ejaculation, peristalsis in the vas results in a post-obstructive dilation, triggering a spasm-related pain [64]. Mesh-related inammatory responses (Sect.

Another CPIP syndrome with both neuropathic and non-neuropathic characteristics is orchialgia [69, 70]. Orchialgia is dened as an intermittent or constant, unilateral or bilateral testicular pain [69]. Sometimes orchialgia is accompanied by dysejaculation [64]. Its aetiology and innervation of the testis are complex. Pain in the testes and epididymides is mediated by the autonomic nerve bres that run along the internal spermatic ves­sels and on the surface of the vas deferens (so­called perivasal nerves), from the pelvic plexus originating in the Th10 to Th12 (testes) and Th12 to L1 segments (epididymides) [69, 70]. Since periprostatic application of local anaesthetics may relieve orchialgia, the idea is supported that the pelvic plexus supplies neural input to the tes­tes [69]. The perivasal nerves may be injured dur­ing hernia repair by various ways including dissection of the spermatic cord or entrapment of

the vas during open hernia repair techniques [70]. Injury due to the preperitoneal dissection or dis­ruption of the autonomic bres accompanying the vas can occur during laparo-endoscopic repairs, as well as placement of the mesh or addi­tional xation materials in proximity to these structures [54, 70–72]. As mentioned before, orchialgia is a combined CPIP syndrome that can include both neuropathic and nociceptive charac­teristics. The nociceptive causes for orchialgia are diverse and include postherniorrhaphy testic­ular ischemia, oedema, brosis of the spermatic cord and infection [70].

pain following a standard hernia repair develops later in the course of recovery or if pain persists after 3–6 months, a concise patient history and physical examination should indicate whether a patient suffers from neuropathic pain, from a nociceptive/inammatory pain (either mesh related or by other origins) or a combination of these or from pain due to a recurrent hernia. However, the differential diagnosis for groin pain in general is extensive, and not all CPIP does nec-

Mesh-related CPIP is suspected when patients complain of a foreign body sensation or feeling of tightness in the groin area [28]. The pain is often aggravated during car driving or leg cross­ing (pressurizing the groin), whereas a supine position relieves mesh-related pain [28]. The same set of nociceptive pain characteristics are present in patients with a meshoma.

When patients or their partners notice an abnormal gait, musculoskeletal origins such as adductor tendinopathy or periostitis pubis (pubal­gia) should be considered. Adductor tendinopa­thy typically relieves during rest and increases during physical activity when using the hip adductor muscles (in particular climbing stairs). The chance on these syndromes increases with the duration of CPIP. Excluding other disorders may lead to the diagnosis of more rare pain syn­dromes such as iliopectineal bursitis.

On the other hand, sexual complaints includ­ing dysejaculation are solely diagnosed on the basis of patient history taking since no physical ndings can be noted. An intense burning, pain­ful sensation that occurs just before, during or after ejaculation [64] conrms the diagnosis of dysejaculation. Orchialgia is experienced as an intermittent, squeezing, deep ache in the testis

The French Neuropathic Pain Group developed a questionnaire (DN4) discriminating between neuropathic and non-neuropathic pain syndromes [79]. The DN4 questionnaire consists of both sensory descriptors and characteristics during physical examination [79]. This questionnaire was tested in a variety of neuropathic pain syn­dromes and demonstrated to be valid. Whether the questionnaire is also usable for distinguishing neuropathic from non-neuropathic CPIP patients needs to be investigated.

An area of sensory decit can be assessed by touching the skin of the alleged painful area with a cotton swab or gauze (Fig.41.6). If the patient experiences a normal sensation in the area of pain, as compared to the contralateral side, neu­ropathic pain becomes less likely. Hypoaesthesia (reduced response to non-painful stimuli) is pres­ent if a reduced perception or numbness is expe­rienced. This by itself can of course be present in any groin scar after hernia surgery. Nevertheless, patients with groin pain and hypoaesthesia expe­rience this type of numbness as (very) annoying. Conversely, hyperaesthesia is present when an increased sensation to non-painful stimuli is reported. Allodynia can be tested likewise, but the stimulus evokes severe pain. When a sharp,