The origins of the vast majority of congenital oculomotor palsies are unknown, or idiopathic to use the medical term. There is some evidence of a familial tendency to the condition, particularly to a partial palsy involving the superior division of the nerve with an autosomal recessive inheritance. The condition can also result from aplasia or hypoplasia of one or more of the muscles supplied by the oculomotor nerve. It can also occur as a consequence of severe birth trauma.

Because the nerve emerges near the bottom of the brain, it is often the first nerve compressed when there is any rise in intracranial pressure. Different presentations of the condition, or associations with other conditions, can help to localize the site of the lesion along the VIth cranial nerve pathway.

The most common causes of VIth nerve palsy in adults are:

- More common: Vasculopathic (diabetes, hypertension, atherosclerosis), trauma, idiopathic.

- Less common: Increased intracranial pressure, giant cell arteritis, cavernous sinus mass (e.g. meningioma, Brain stem Glioblastoma aneurysm, metastasis), multiple sclerosis, sarcoidosis/vasculitis, postmyelography, lumbar puncture, stroke (usually not isolated), Chiari Malformation, hydrocephalus, intracranial hypertension, tuberculosis meningitis.

In children, Harley reports typical causes as traumatic, neoplastic (most commonly brainstem glioma), as well as idiopathic. Sixth nerve palsy causes the eyes to deviate inward (see: Pathophysiology of strabismus). Vallee et al. report that benign and rapidly recovering isolated VIth nerve palsy can occur in childhood, sometimes precipitated by ear, nose and throat infections.

Oculomotor palsy can arise as a result of a number of different conditions. Non traumatic pupil-sparing oculomotor nerve palsies are often referred to as a 'medical third' with those affecting the pupil being known as a 'surgical third'.

Other causes may include:

- Diabetes mellitus

- Facial nerve paralysis, sometimes bilateral, is a common manifestation of sarcoidosis of the nervous system, neurosarcoidosis.

- Bilateral facial nerve paralysis may occur in Guillain–Barré syndrome, an autoimmune condition of the peripheral nervous system.

- Moebius syndrome is a bilateral facial paralysis resulting from the underdevelopment of the VII cranial nerve (facial nerve), which is present at birth. The VI cranial nerve, which controls lateral eye movement, is also affected, so people with Moebius syndrome cannot form facial expression or move their eyes from side to side. Moebius syndrome is extremely rare, and its cause or causes are not known.

Central facial palsy can be caused by a lacunar infarct affecting fibers in the internal capsule going to the nucleus. The facial nucleus itself can be affected by infarcts of the pontine arteries.

The prognosis of a lesion in the visual neural pathways that causes a conjugate gaze palsy varies greatly. Depending on the nature of the lesion, recovery may happen rapidly or recovery may never progress. For example, optic neuritis, which is caused by inflammation, may heal in just weeks, while patients with an ischemic optic neuropathy may never recover.

The number of new cases of Bell's palsy is about 20 per 100,000 population per year. The rate increases with age. Bell’s palsy affects about 40,000 people in the United States every year. It affects approximately 1 person in 65 during a lifetime.

A range of annual incidence rates have been reported in the literature: 15, 24, and 25–53 (all rates per 100,000 population per year). Bell’s palsy is not a reportable disease, and there are no established registries for people with this diagnosis, which complicates precise estimation.

The facial nerve is the seventh of 12 cranial nerves. This cranial nerve controls the muscles in the face. Facial nerve palsy is more abundant in older adults than in children and is said to affect 15-40 out of 100,000 people per year. This disease comes in many forms which include congenital, infectious, traumatic, neoplastic, or idiopathic. The most common cause of this cranial nerve damage is Bell's palsy (idiopathic facial palsy) which is a paralysis of the facial nerve. Although Bell's palsy is more prominent in adults it seems to be found in those younger than 20 or older than 60 years of age. Bell's Palsy is thought to occur by an infection of the herpes virus which may cause demyelination and has been found in patients with facial nerve palsy. Symptoms include flattening of the forehead, sagging of the eyebrow, and difficulty closing the eye and the mouth on the side of the face that is affected. The inability to close the mouth causes problems in feeding and speech. It also causes lack of taste, acrimation, and sialorrhea.

The use of steroids can help in the treatment of Bell's Palsy. If in the early stages, steroids can increase the likelihood of a full recovery. This treatment is used mainly in adults. The use of steroids in children has not been proven to work because they seem to recover completely with or without them. Children also tend to have better recovery rates than older adults. Recovery rate also depends on the cause of the facial nerve palsy (e.g. infections, perinatal injury, congenital dysplastic). If the palsy is more severe patients should seek steroids or surgical procedures. Facial nerve palsy may be the indication of a severe condition and when diagnosed a full clinical history and examination are recommended.

Although rare, facial nerve palsy has also been found in patients with HIV seroconversion. Symptoms found include headaches (bitemporal or occipital), the inability to close the eyes or mouth, and may cause the reduction of taste. Few cases of bilateral facial nerve palsy have been reported and is said to only effect 1 in every 5 million per year.

The efficacy of acupuncture remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices). There is very tentative evidence for hyperbaric oxygen therapy in severe disease.

The cause of congenital fourth nerve palsy is unclear in most cases. It may be neurogenic in origin, due to a dysgenesis of the CN IV nucleus or nerve, but a clinically similar palsy may result from absence or mechanical dysfunction (e.g., abnormal laxity) of the superior oblique tendon. Usually unilateral, congenital fourth nerve palsies can also occur bilaterally. Bilateral congenital fourth nerve palsy may be unmasked only after corrective surgery of one eye for what was thought to be a unilateral palsy.

The VIth nerve's course is short and lesions in the orbit rarely give rise to isolated VIth nerve palsies, but more typically involve one or more of the other extraocular muscle groups.

- "For acquired fourth nerve palsy, see fourth nerve palsy"

Congenital fourth nerve palsy is a condition present at birth characterized by a vertical misalignment of the eyes due to a weakness or paralysis of the superior oblique muscle.

Other names for fourth nerve palsy include superior oblique palsy and trochlear nerve palsy.

When looking to the right/left the nerve/muscle isn't strong enough or is too long and the eye drifts up.

Cranial nerve disease is an impaired functioning of one of the twelve cranial nerves. Although it could theoretically be considered a mononeuropathy, it is not considered as such under MeSH.

It is possible for a disorder of more than one cranial nerve to occur at the same time, if a trauma occurs at a location where many cranial nerves run together, such as the jugular fossa. A brainstem lesion could also cause impaired functioning of multiple cranial nerves, but this condition would likely also be accompanied by distal motor impairment.

A neurological examination can test the functioning of individual cranial nerves, and detect specific impairments.

There is no treatment of conjugate gaze palsy itself, so the disease or condition causing the gaze palsy must be treated, likely by surgery. As stated in the causes section, the gaze palsy may be due to a lesion caused by stroke or a condition. Some of the conditions such as Progressive supra nuclear palsy are not curable, and treatment only includes therapy to regain some tasks, not including gaze control. Other conditions such as Niemann-Pick disease type C have limited drug therapeutic options. Stroke victims with conjugate gaze palsies may be treated with intravenous therapy if the patent presents early enough, or with a surgical procedure for other cases.

Fourth cranial nerve palsy also known as Trochlear nerve palsy, is a condition affecting Cranial Nerve 4 (IV), the Trochlear Nerve, which is one of the Cranial Cranial Nerves that causes weakness or paralysis to the Superior Oblique Muscle that it innervates. This condition often causes vertical or near vertical double vision as the weakened muscle prevents the eyes from moving in the same direction together.

Because the fourth cranial nerve is the thinnest and has the longest intracranial course of the cranial nerves, it is particularly vulnerable to traumatic injury.

To compensate for the double-vision resulting from the weakness of the superior oblique, patients characteristically tilt their head down and to the side opposite the affected muscle.

When present at birth, it is known as congenital fourth nerve palsy.

In some cases, spastic cerebral palsy is caused by genetic factors.

The genetic factors for spastic cerebral palsy include:

Although it has its origins in a brain injury, spastic CP can largely be thought of as a collection of orthopaedic and neuromuscular issues because of how it manifests symptomatically over the course of the person's lifespan. It is therefore not the same as "brain damage" and it need not be thought of as such. Spastic quadriplegia in particular, especially if it is combined with verbal speech challenges and strabismus, may be misinterpreted by the general population as alluding to cognitive dimensions to the disability atop the physical ones, but this is false; the intelligence of a person with any type of spastic CP is unaffected by the condition "of the spasticity itself".

In spastic cerebral palsy in children with low birth weights, 25% of children had hemiplegia, 37.5% had quadriplegia, and 37.5% had diplegia.

The cause of PBP is unknown. One form of PBP is found to occur within patients that have a CuZn-superoxide dismutase (SOD1) mutation. Progressive bulbar palsy patients that have this mutation are classified with FALS patients, Familial ALS (FALS) accounts for about 5%-10% of all ALS cases and is caused by genetic factors. Within these, about 20-25% are linked to the SOD1 mutation. It is not currently known if and how the decreased SOD1 activity contributes to Progressive Bulbar Palsy or FALS, and studies are being done in patients and transgenic mice to help further understand the impact of this gene on the disease.

A case study was done on a 42-year-old woman who complained of muscle weakness 10 months prior to admission in the hospital. Upon neurological examination, the patient showed muscle atrophy, fasciculation in all limbs and decreased deep tendon reflexes. The patient’s older brother, father, and paternal uncle had previously all died of ALS or an ALS type syndrome. The patient developed Progressive Bulbar Palsy, became dependent on a respirator, and had two episodes of cardiac arrest. The patient died from pneumonia two years after the onset of the disease. After studying the patient, it was found that the patient had a two base pair deletion in the 126th codon in exon 5 of the SOD1 gene. This mutation produced a frameshift mutation, which led to a stop codon at position 131. SOD1 activity was decreased by about 30%. The patient’s histological examination showed severe reduction in lower motor neurons. Upon further study, this case proved to be important because it demonstrated that SOD1 mutations might not effect steady neuropathological changes, and that environmental and genetic factors might affect the phenotype of the SOD1 mutations.

Almost all cases of synkinesis develop as a sequel to nerve trauma (the exception is when it is congenitally acquired as in Duane-Retraction Syndrome and Marcus Gunn phenomenon). Trauma to the nerve can be induced in cases such as surgical procedures, nerve inflammation, neuroma

, and physical injury.

The muscle spasticity can cause gait patterns to be awkward and jerky. The constant spastic state of the muscle can lead to bone and tendon deformation, further complicating the patient's mobility. Many patients with spastic hemiplegia are subjected to canes, walkers and even wheelchairs. Due to the decrease in weight bearing, patients are at a higher risk of developing osteoporosis. An unhealthy weight can further complicate mobility. Patients with spastic hemiplegia are a high risk for experiencing seizures. Oromotor dysfunction puts patients at risk for aspiration pneumonia. Visual field deficits can cause impaired two-point discrimination. Many patients experience the loss of sensation in the arms and legs on the affected side of the body. Nutrition is essential for the proper growth and development for a child with spastic hemiplegia.

Parinaud's Syndrome results from injury, either direct or compressive, to the dorsal midbrain. Specifically, compression or ischemic damage of the mesencephalic tectum, including the superior colliculus adjacent oculomotor (origin of cranial nerve III) and Edinger-Westphal nuclei, causing dysfunction to the motor function of the eye.

Classically, it has been associated with three major groups:

1. Young patients with brain tumors in the pineal gland or midbrain: pinealoma (intracranial germinomas) are the most common lesion producing this syndrome.

2. Women in their 20s-30s with multiple sclerosis

3. Older patients following stroke of the upper brainstem

However, any other compression, ischemia or damage to this region can produce these phenomena: obstructive hydrocephalus, midbrain hemorrhage, cerebral arteriovenous malformation, trauma and brainstem toxoplasmosis infection. Neoplasms and giant aneurysms of the posterior fossa have also been associated with the midbrain syndrome.

Vertical supranuclear ophthalmoplegia has also been associated with metabolic disorders, such as Niemann-Pick disease, Wilson's disease, kernicterus, and barbiturate overdose.

In the industrialized world, the incidence of overall cerebral palsy, which includes but is not limited to spastic diplegia, is about 2 per 1000 live births. Thus far, there is no known study recording the incidence of CP in the overall nonindustrialized world. Therefore, it is safe to assume that not all spastic CP individuals are known to science and medicine, especially in areas of the world where healthcare systems are less advanced. Many such individuals may simply live out their lives in their local communities without any medical or orthopedic oversight at all, or with extremely minimal such treatment, so that they are never able to be incorporated into any empirical data that orthopedic surgeons or neurosurgeons might seek to collect. It is shocking to note that—as with people with physical disability overall—some may even find themselves in situations of institutionalization, and thus barely see the outside world at all.

From what "is" known, the incidence of spastic diplegia is higher in males than in females; the Surveillance of Cerebral Palsy in Europe (SCPE), for example, reports a M:F ratio of 1.33:1. Variances in reported rates of incidence across different geographical areas in industrialized countries are thought to be caused primarily by discrepancies in the criteria used for inclusion and exclusion.

When such discrepancies are taken into account in comparing two or more registers of patients with cerebral palsy and also the extent to which children with mild cerebral palsy are included, the incidence rates still converge toward the average rate of 2:1000.

In the United States, approximately 10,000 infants and babies are born with CP each year, and 1200–1500 are diagnosed at preschool age when symptoms become more obvious. It is interesting to note that those with extremely mild spastic CP may not even be aware of their condition until much later in life: Internet chat forums have recorded men and women as old as 30 who were diagnosed only recently with their spastic CP.

Overall, advances in care of pregnant mothers and their babies has not resulted in a noticeable decrease in CP; in fact, because medical advances in areas related to the care of premature babies has resulted in a greater survival rate in recent years, it is actually "more" likely for infants with cerebral palsy to be born into the world now than it would have been in the past. Only the introduction of quality medical care to locations with less-than-adequate medical care has shown any decreases in the incidences of CP; the rest either have shown no change or have actually shown an increase. The incidence of CP increases with premature or very low-weight babies regardless of the quality of care.

Progressive Bulbar Palsy is slow in onset, with symptoms starting in most patients around 50–70 years of age. PBP has a life expectancy typically between 6 months and 3 years from onset of first symptoms. It is subtype of the Motor Neurone Diseases (MND) accounting for around 1 in 4 cases. Amyotrophic lateral sclerosis (ALS) is another sub-type. Pure PBP without any EMG or clinical evidence of abnormalities in the legs or arms is possible, albeit extremely rare. Moreover, about twenty-five percent of patients with PBP eventually develop the widespread symptoms common to ALS.

The incidence of cerebral palsy has increased in the past 40 years. It has been estimated that in the United States cerebral palsy occurs in 4 out every 1000 births. Of these births about 20–30% of them have spastic hemiplegia. Spasticity overall, is the more common type of cerebral palsy, whereas as non-spastic cerebral palsy is less common. Studies show that spastic type cerebral palsy is on the rise, and the occurrence of diplegia type is decreasing. The prevalence of cerebral palsy is higher in areas of low socioeconomic status. This could potentially be because cerebral palsy incidence increases as birth weight decreases.

Synkinesis is the result from miswiring of nerves after trauma. This result is manifested through involuntary muscular movements accompanying voluntary movements. For example, voluntary smiling will induce an involuntary contraction of the eye muscles causing the eye to squint when smiling. Most commonly involved are facial muscles and the extraocular muscles, rarely the hands are performing mirror movements.

Causes are diverse and include nerve trauma with improper healing, or nerve degeneration, as in the course of Parkinson´s disease. In congenital cases, mutations of genes involved in nerve growth, specifically axonal growth have been found. Rarely, it is part of syndromes with neuroendocrine problems such as Kallman syndrome.

The prognosis is usually good with normal intelligence and lifespan. Treatment depends on the cause, but is largely conservative with facial retraining or mime therapy, if needed, while Botox and surgery are used as last resort.

There have been cases of improvement in extra-ocular movement with botulinum toxin injection.