Sexual Dysfunction in Patients with Neurological Disorders

Upper and lower motor neuron neurophysiology and motor control

This chapter considers the principles that underlie neurophysiological studies of upper motor neuron or lower motor neuron lesions, based on an understanding of the normal structure and function of the motor system. Human motor neurophysiology consists of an evaluation of the active components of the motor system that are relevant to volitional movements. Relatively primitive motor skills include locomotion, much dependent on the spinal cord central pattern generator, reaching, involving proximal and distal muscles activation, and grasping. Humans are well prepared to perform complex movements like writing. The role of motor cortex is critical for the motor activity, very dependent on the continuous sensory feedback, and this is essential for adapting the force and speed control, which contributes to motor learning. Most corticospinal neurons in the brain project to brainstem and spinal cord, many with polysynaptic inhibitory rather than excitatory connections. The monosynaptic connections observed in humans and primates constitute a specialized pathway implicated in fractional finger movements. Spinal cord has a complex physiology, and local reflexes and sensory feedback are essential to control adapted muscular contraction during movement. The cerebellum has a major role in motor coordination, but also consistent roles in sensory activities, speech, and language, in motor and spatial memory, and in psychological activity. The motor unit is the final effector of the motor drive. The complex interplay between the lower motor neuron, its axon, motor end-plates, and muscle fibers allows a relevant plasticity in the movement output.

Sexuality and intimacy in ALS: systematic literature review and future perspectives

Several features of amyotrophic lateral sclerosis (ALS) impact on sexuality and intimate relationship; however, the issue has received poor attention so far. We performed a systematic literature review in order to provide an up-to-date account of sexuality in ALS. References were identified by searches of PubMed, Web of Science, Scopus and PsycINFO (1970-2017, English literature). The following were the key terms: 'sexual' OR 'sexuality' OR 'intimacy' OR 'marital' AND 'ALS' OR 'Amyotrophic Lateral Sclerosis' OR 'Motor Neuron Disease' OR 'MND'. Titles and abstracts were screened for relevance and a full-text analysis was performed on the selected articles. Studies were included if they referred to sexual well-being/activities/functions or intimate relationship between patients and their partners and management of such topic by clinicians. Eligibility assessment was performed independently by two reviewers. A thematic and level of evidence classification of studies was performed. Studies' design, objectives, measurements and outcomes were summarised. Thirty articles were included and four topics were identified: intimacy in the dyads; sexual activities in patients and with their partners; sexual function disturbances; and sexuality and cognitive-behavioural alterations. The quality of the studies varies, with globally poor level of evidence. Some sexuality issues have been only sparsely addressed, such as gender-related differences, same-sex relationships and sexual activities other than intercourse. Sexuality in ALS is still not adequately considered by clinicians and researchers. We present preliminary recommendations for improving sexuality and intimacy at any ALS multidisciplinary clinics.

Prevalence of Sexual Dysfunctions Among Women with Multiple Sclerosis

Sexual concerns are known to be common in women suffering from multiple sclerosis (MS) but definite data on the prevalence of particular sexual dysfunctions (SD) remain unclear. Previous studies brought inconsistent findings and rely on small groups of patients or use of unvalidated assessment methods. The aim of this research was to evaluate the prevalence of SD in women with MS using validated clinimetric scales. 137 female inpatients with MS diagnosis were interviewed, completed The Female Sexual Function Questionnaire SFQ28 and underwent neurological assessment. Only 2.2 % of patients had ever discussed their sexual concerns with a physician. 70.1 % reported sexual activity. At least one SD could be found in 82.5 % of patients, hypoactive sexual desire (57.7 %), arousal dysfunction (decreased genital sensation in 47.3 %, decreased lubrication in 48.4 %, decreased subjective arousal in 45.2 %) and orgasmic dysfunction (39.8 %) being the most probable. SD were less likely in women who assessed their relationship positively but more common in older patients and those who had a positive history of depression. The prevalence of SD was higher comparing to the majority of studies by other authors. In conclusion, SD are very common in female patients with MS and permanently overlooked by medical professionals. Therefore, the assessment of sexual function should be implemented in all patients after the diagnosis of MS. Further research is needed for better understanding of the sexuality of this particular population in order to establish targets for therapeutic intervention.

The dual control model of male sexual response: a theoretical approach to centrally mediated erectile dysfunction

A theoretical model of dual control of male sexual response is considered, based on the balancing of central excitation and inhibition, with individuals varying in their propensity for both sexual excitation and inhibition of sexual response. A questionnaire method for measuring propensities for sexual excitation and inhibition has been developed (SIS/SES questionnaire), resulting in one excitation factor (SES) and two inhibition factors (SIS1 and SIS2). Evidence for the existence of both inhibitory and excitatory tone is discussed. The first inhibition factor (SIS1) may be related to level of inhibitory tone and is associated with fear of performance failure. The second inhibition factor (SIS2) may be related to external threats (e.g. from within the sexual relationship). The implications for the treatment of centrally mediated erectile dysfunction are discussed, with predictions that high SIS2 individuals will respond to psychological treatment, whereas high SIS1 individuals will respond better to pharmacological methods of treatment.

Pharmacologic Treatment of Cognitive Deficits and Hypersexuality Due to “Shaken-Baby Syndrome”

Objective:

To describe the clinical effects of amantadine and propranolol in an agitated pediatric patient with cognitive deficits, hyperactivity, and hypersexualism secondary to “shaken-baby syndrome.”

Background:

Patients with shaken-baby syndrome can present with cognitive and behavioral impairments.

Case:

A 9-year-old girl presented with cognitive impairments secondary to shaken-baby syndrome at 3 weeks of age. She was receiving many medications, including dextroamphetamine, methylphenidate, and clonidine, that were not effective in improving her cognitive status or decreasing her hypersexuality. She was weaned from stimulants and clonidine and prescribed amantadine 100 mg bid with improvement of attention, concentration, and cognition, although hypersexuality remained. She was then started on propranolol 10 mg tid and a gradual increase to 40 mg tid with amelioration of hypersexuality and hyperactivity and no unwanted effects noted. Self-weaning of propranolol was associated with the return of hypersexuality. The combination of amantadine and propranolol led to improvement of cognition and behavior, especially intellectual functioning and appropriate socialization with peers, respectively.

Conclusion:

Cognitive deficits and hypersexuality with hyperactive features due to shaken-baby syndrome may respond to the drug regimen of amantadine and propranolol.

Central inhibition of sexual response in the male: a theoretical perspective

A theoretical model for central inhibition of sexual response is proposed, postulating individual variability in the propensity for such inhibition. Whereas such inhibition is typically adaptive, individuals with high propensity may be vulnerable to sexual dysfunction, and those with low propensity to high risk sexual behavior. Evidence of the existence and localization of such inhibitory mechanisms from both the animal and human literature is reviewed. Evidence of central neurotransmitters with sexual inhibitory effects is substantial, though in most cases the inhibition is not specific to sexual response or behavior. Recent studies have identified centers in the brain stem and lateral hypothalamus which appear to have specific inhibitory effects on sexual response. A variety of adaptive mechanisms involving inhibition of sexual response are considered, some involving perception of threat, others occurring more directly as consequences of previous sexual activity. These different adaptive functions may well involve different inhibitory mechanisms. This theoretical model opens a new agenda for experimental research into adaptive sexual behavior, both human and animal.

A review of the effect of traumatic brain injury on the human sexual response

A human sexual response format was used to describe possible sexual dysfunctions after TBI. Additional material was also included to qualify the information drawn from the above format. A number of possible conclusions were drawn, indicating that the causes and effects of sexual functioning after TBI are very confusing and that the literature does not clarify this confusion. One cannot accurately differentiate between primary and secondary sexual problems and, therefore, cannot evaluate the contribution of each problem to the presented sexual dysfunction.

Sexual function in women with advanced multiple sclerosis

Changes in sexual function in 47 women with advanced multiple sclerosis are described. Twenty eight (59.6%) of the women reported decreased sexual desire. Seventeen (36.2%) reported decreased lubrication. Five (10.6%) others did not know if they lubricated or not. Eighteen women (38.3%) reported diminished orgasmic capacity and six (12.8%) others had never had an orgasm. Sensory dysfunction in the genital area was experienced by 61.7% of the women and 76.6% had weakness of the pelvic muscles. Sixty six per cent had bowel problems and 89.4% had bladder dysfunction. The changes in sexual function correlated both with neurological symptoms from the sacral segments, such as weakness of the pelvic floor and bladder and bowel dysfunction, and to other symptoms such as ataxia and vertigo as well as with age and the occurrence of amenorrhoea. A significant correlation was found between expanded disability status scale (EDSS) score and cohabitation. Problems with sexual function were reported significantly more often by women with lower EDSS scores. Most women (83%) found the interview a positive experience.

Placing erection in context: the reflexogenic-psychogenic dichotomy reconsidered

Penile erections are usually classified as arising from "reflexogenic" or "psychogenic" causes. In practice this dichotomy has translated, somewhat circularly, to a distinction between spinal vs. supraspinal mediation, pelvic vs. hypogastric neural mediation, and perineal somesthetic stimulation vs. stimulation of receptors innervated by the cranial nerves. Evidence for differential regulation of erection in different contexts is reviewed. Research ascribing a physiological role to the hypogastric nerves in psychogenic erection, exemplified by classic studies of cats and spinally injured men, is suggestive but not compelling. Somewhat stronger is evidence that erection in some contexts (e.g., nocturnal penile tumescence (NPT) in humans or touch-stimulated erection in rats) is more sensitive to androgen levels than in other contexts (e.g., visual erotic stimuli in men or copulation in rats). However, some of these differences may arise from the relative erectogenic strength of the stimuli, rather than from qualitative differences in androgen sensitivity of different contexts. More compelling is the possibility that conflicting interpretations of the role of dopamine in erection may stem in large part from differences among laboratories in the context in which erection is evoked. In light of the evidence reviewed, it seems unlikely that the conventional reflexogenic-psychogenic dichotomy should be retained, at least in its present form. As a first step, it may be worth considering that reflexive erections may not be limited to somesthetic perineal stimulation, but rather may also include stimuli received via the cranial nerves. Two alternatives to the standard reflexogenic-psychogenic dichotomy are proposed. The first is a minor revision in which two senses of psychogenic erection are distinguished: the weak, commonly used, sense would include erection resulting from any extrinsic nonsomesthetic stimulation, whether visual, auditory, or chemosensory. In this sense, reflexive erections and psychogenic erections may not be mutually exclusive. The strong sense of psychogenic erection would be limited to memory and fantasy. The origins of psychogenic erection in both senses need not be available to consciousness, which may account for apparently spontaneous erections. In the second alternative taxonomy, erectogenic stimuli are classified as contact (somesthetic) or noncontact, and their action in evoking erection is placed on a continuum of reflexivity. Erectile contexts could then be considered as orthogonal to the other two dimensions. Even without a change in taxonomy, the conduct and interpretation of research into erectile function may be expected to benefit from closer attention to differences and similarities between contexts and species, and to context-sensitive differences in the regulation of erection.