The neurophysiology of sex 

Sexuality is part of being human. Our sexuality affects how individuals perceive themselves 
and how they interact with those around them. Sexuality is a complex area of functioning encompassing sexual development which begins in utero; sexual awareness which develops through childhood and adolescence; sexual responsiveness and awareness (Bancroft J 2009).

It is a key element in the formation of meaningful relationships in adult life. It is an area of strength but also of vulnerability to internal and external factors such as health, self-esteem, societal and family pressures and values.


At the most basic level, sexuality is the means by which a partner is found for reproduction and the passing on of genetic material and this is evident in the animal kingdom as a whole.

However, for humanity, it is about relationships. Neurological trauma or illness can have a
major impact on sexual responsiveness and the capacity for relationships.
More often than not sexual expression is something that occurs within a relationship.

Part of the normal sexual experience
includes masturbation and fantasy but it is in relationships that sexual expression is generally fulfilled.

Why relationships matter 

The dynamics of a relationship have a profound effect on sexual functioning. Sexual expression begins with desire which is a function of
the brain.

Within the neural pathways there are both inhibitory and excitatory neurotransmitters. Dopamine is excitatory
and Serotonin is inhibitory in the pathways linking desire to arousal of the autonomic and peripheral nervous system.

Desire is influenced by a variety of cognitions and emotions such
as mood – excited, happy, fearful, oppressed memories of previous good sexual experience or memories of painful abusive relationships.

 It will be affected by fatigue which is a very common symptom of neurological disease or trauma. It may be influenced by social context – is this relationship developing in a private setting or is it within a nursing home where privacy is diffcult to establish?


The most recent imaging studies have demonstrated that certain parts of the brain are active in sexual desire, including the anterior cingulate cortex which connects to the amygdala, which in turn has a key role in emotional responsiveness (Zeki A 2007).

The central nervous system, through a complex set of pathways involving the higher levels
of cortical functioning, provides a delicately balanced system to allow sexual expression within relationships.

Any part of the system can be affected by physical, psychological, social and emotional factors.

The brain in turn connects through the spinal cord to the periphery. The sacral segment of the spinal cord is a key area from which nerves travel to the genitalia. The parasympathetic output to the genitalia comes from the sacral cord and the sympathetic nerve supply from the thoracic and upper lumbar cord.

In response to sexual arousal the nervous system connects to the genitalia via the spinal cord leading to a neurovascular response
with the parasympathetic nerves triggering erection in the male and vasocongestion in the female.

The sympathetic system is involved in ejaculation. Any disease or trauma to the nervous system or medications acting on the nervous system can interrupt the pathways. For example, a thoracic spinal cord injury will separate the sacral spinal cord from control by higher centres so that in the male reflex erections may still occur in response to a variety of stimuli including full bladder or irritation to the skin, but psychogenic erections in response to sexual desire may not occur.

What makes a good couple? 

Key factors include mutual attraction, love, having fun together, enjoying sex together, trusting each other, ease of communication
and being special to each other.

As relationships move into longer term commitments, there are additional factors, including shared experiences and future plans, hopes and expectations.

Demands are placed on relationships such as financial commitments, bringing up children, looking after elderly relatives.

Meanwhile, each individual brings into that relationship their own health, beliefs, values
and approaches to managing stress; their past experiences both good and bad, their need for autonomy and their need for intimacy.

Each person has their own self-image and an image of their partner, which can be quite different to how other people see them. Impacting on the relationship are external pressures which can
be social, financial, work and family pressures.

Many factors can challenge the dynamic balance of the relationship and the onset of disease or trauma can have a profound impact.

When everything changes…

The context of most sexual expression is within a relationship. It is also within this context that many people will experience the life-changing impact of chronic disease or acquired disability.

For some couples, problems of adjustment to the changes can be significant and place a strain on the relationship, sometimes leading
to separation. For others, the impact of such stress can enhance their closeness.

Different roles tend to be assumed as a relationship progresses. One of the commonest divisions of roles within a long-term relationship is with 
the arrival of children when, in some cases, one partner assumes the ‘bread-winner’ role and the other home-maker. 

Each partner has an image of self and of their partner, and this includes an awareness of their physical and psychological health. The onset of neurological disease and/or disability can present a great challenge to the stable state of a relationship. This may result in a change of physical appearance and cognitive ability.

The couple, having been partners in a familiar relationship, may find now that there is a carer and a partner who requires care. New roles may be taken on by one partner whilst roles must be relinquished by the other.

The shared hopes and expectations for the future may alter. It is important to note that the greatest impact comes from disorders that alter cognitive and emotional responses – rather than just physical functioning.

Escalating problems 

Most often, the problems are multi-factorial
in origin. For example, there could be loss of sensation because of MS, which alters the sexual experience, together with fatigue causing a change in overall lifestyle; low mood as a response to loss; medication resulting in specific sexual dysfunction, such as delayed orgasm with the selective serotonin reuptake inhibitors (SSRI anti-depressants); social changes resulting from the loss of income; or practical issues at home, such as no longer managing stairs and therefore, sleeping in a separate room from the partner.

Brain injuries can also lead to impaired self-monitoring, which means the individual
may be unable to suppress commenting on things that come to mind no matter how offensive they may be. Self-centredness is also
a common trait, as is a lack of empathy.

The ability to take note of how the other person
is feeling – whether they’ve had a good or a
bad day – without speaking to them, is quite important in relationships.

With acquired brain injury, non-verbal questioning can be lost (Wood R Williams C 2008).
Sexual problems are common post brain
injury and, in one study, 50% of men identified dysfunction (O’Carroll et al. 1991).

In a minority of patients, increased sexual drive and sexual dis-inhibition can be a problem.

This is more likely to occur with damage to the frontal
lobes. Reduced sexual desire and interest
are most common and result from the brain damage itself, the effect on the relationship, fatigue, depression, anxiety, low motivation and, sometimes, low testosterone secondary to damage to the hypothalamic pituitary tract.

The partner’s plight 

A common observation from partners of people with acquired brain injury is ‘this is not the person I married’. Often in relationships, partners face challenges together. In the event of a trauma, the able-bodied partner may face this new challenge alone.

While this is going on they may also feel a
desire to grieve for the old loved one they have lost. But there is no acceptable way for them 
to do this.


They may feel isolated and in a state of social limbo, in which it feels inappropriate to go out and have fun without their partner. Also, friends may say that the patient looks good, but only the partner sees the major behavioural changes that have occurred.
Sometimes we see situations where the relationship had been on the verge of splitting up before the injury or onset of disease.

With the patient, unable to make the decision to end the relationship afterwards, the partner becomes trapped in a loveless or failing relationship
out of guilt.

Rebuilding relationships 

Despite all the pressures trauma and neurological conditions can put on a couple, relationships can be rebuilt. In relationship therapy, we are always honest and explain that things will never get back to how they were.

But, for all the behavioural changes, there
may be factors that the partner still finds very attractive. We encourage couples to find new ways to have fun together and to start getting to know one another from scratch.

Other interventions 

For men, drugs such as phosphodiesterase inhibitors have proved to be useful treatments for erectile dysfunction.
These work on the relaxation of smooth muscle which allows vasocongestion in the genitalia in response to a chemical messenger cyclic GMP. 

However, it is always important to approach treatment of sexual disorders in a holistic manner. It is rarely simply a mechanical problem that can be fixed with a pill.


Therefore, taking a full history and if possible seeing the individual with their partner
allows the psychosocial aspects of the sexual dysfunction to be explored as well as the physical aspects.


Healthcare professionals need to be alert to the stresses and strains that can be experienced in this area of life which generally people view as very private and personal.

The P-LI-SS-IT model (Annon 1976), which
was proposed over 40 years ago, emphasised that the first and most helpful approach to
sex and relationship problems was giving people permission (P) to speak about the issues.

People may drop hints that all is not well in a relationship and it is up to the health professional to pick up on that hint.


Even if you are not certain how to help, acknowledge that there is an issue; allow the individual to talk about it and then, if you feel it is beyond your remit or skill, offer to refer to another agency – perhaps to the GP or to a sex and relationships clinic or to an organisation such as Relate.

The most important response is to say, “this is a valid issue to raise and there is help available”. In the PLISSIT model the next three stages are the provision of Limited Information, Specific Suggestions and Intensive Therapy. Most people will be helped in the first one or two steps of this model.

TEN STEPS: How healthcare professionals should approach their patients’ intimate relationship problems. 

  1. Be honest and realistic with patients and partners. They may never recover their old relationship, but could still build a positive new one.
  2. Consider the difficulties the partner may be going through and how that may be impacting 
on their health. Do they look exhausted? Have they been crying? A doorstep conversation in private might encourage them to open
 Perhaps ask them if they have considered visiting their GP about their own concerns.
  3. Be careful not to overload partners with too many responsibilities, such as helping out with cognitive therapy at home. Although outwardly willing to help, inside they may be feeling drained, isolated and depressed.
  4. Often patients going through rehab can feel their sexual identity is threatened, leading to low self-esteem. Give them time to do the little things they usually would to look their best.
For women, this might
include shaving their legs or putting make-up on; for men it might be having a shave or doing their hair.
  5. Consider implementing some training on sex and relationship problems within your ward, unit, service or centre.
  6. Remember that, ultimately, your primary responsibility is to get the best outcome for the patient – not to influence whether or not their relationship survives.
  7. Get to know the sources of professional help
available in your local area. Relate is a charity offering relationship support across the UK. Some areas are also served by specialist clinical psychology services. Patients should also be encouraged to consider visiting their GP about such matters.
  8. Remember that sex and relationships are very sensitive topics and most people will not be comfortable talking to strangers about them. Create a safe and secure setting to discuss them. Relationship issues should be presented as a normal and important element of the patient’s overall health and wellbeing.
  9. Always acknowledge there is a problem if
the patient or their partner mentions it or even just 
hints at it.
Never ignore the problem and certainly do not make light of it or embarrass or make fun of the patient.
  • If you suspect there are sex and relationship concerns, try asking a non-threatening question. Perhaps as the patient is leaving, ask how things are at home. This gives them an opportunity to get the issue off their chest without bluntly asking them an awkward question.

Barbara Chandler is a consultant in rehabilitation medicine in NHS Highland. Previously she ran a sex and relationships clinic for people with neurological disability in the North of England. She teaches health and social care professionals on sex and relationship issues and has been published extensively on the topic. 

Useful resources: 

Relate: www.relate.org.uk: www.relate.org.uk
The Institute of Psycho-sexual Medicine: www.ipm.org.uk
The College of sex and Relationship Therapists: www.cosrt.org.uk