Bell's palsy is characterized by a one-sided facial droop that comes on within 72 hours. In rare cases (<1%), it can occur on both sides resulting in total facial paralysis.

The facial nerve controls a number of functions, such as blinking and closing the eyes, smiling, frowning, lacrimation, salivation, flaring nostrils and raising eyebrows. It also carries taste sensations from the anterior two-thirds of the tongue, via the chorda tympani nerve (a branch of the facial nerve). Because of this, people with Bell's palsy may present with loss of taste sensation in the anterior 2/3 of the tongue on the affected side.

Although the facial nerve innervates the stapedial muscles of the middle ear (via the tympanic branch), sound sensitivity and dysacusis are hardly ever clinically evident.

Although defined as a mononeuritis (involving only one nerve), people diagnosed with Bell’s palsy may have "myriad neurological symptoms" including "facial tingling, moderate or severe headache/neck pain, memory problems, balance problems, ipsilateral limb paresthesias, ipsilateral limb weakness, and a sense of clumsiness" that are "unexplained by facial nerve dysfunction".

A tumor compressing the facial nerve anywhere along its complex pathway can result in facial paralysis. Common culprits are facial neuromas, congenital cholesteatomas, hemangiomas, acoustic neuromas, parotid gland neoplasms, or metastases of other tumours.

Often, since facial neoplasms have such an intimate relationship with the facial nerve, removing tumors in this region becomes perplexing as the physician is unsure how to manage the tumor without causing even more palsy. Typically, benign tumors should be removed in a fashion that preserves the facial nerve, while malignant tumors should always be resected along with large areas of tissue around them, including the facial nerve. While this will inevitably lead to heightened paralysis, safe removal of a malignant neoplasm is worth the often treatable palsy that follows. In the best case scenario, paralysis can be corrected with techniques including hypoglossal-facial nerve anastomosis, end-to-end nerve repair, cross facial nerve grafting, or muscle transfer/transposition techniques, such as the gracilis free muscle transfer.

Patients with facial nerve paralysis resulting from tumours usually present with a progressive, twitching paralysis, other neurological signs, or a recurrent Bell's palsy-type presentation.

The latter should always be suspicious, as Bell's palsy should not recur. A chronically discharging ear must be treated as a cholesteatoma until proven otherwise; hence, there must be immediate surgical exploration. Computed tomography (CT) or magnetic resonance (MR) imaging should be used to identify the location of the tumour, and it should be managed accordingly.

Other neoplastic causes include leptomeningeal carcinomatosis.

Once the facial paralysis sets in, many people may mistake it as a symptom of a stroke; however, there are a few subtle differences. A stroke will usually cause a few additional symptoms, such as numbness or weakness in the arms and legs. And unlike Bell's palsy, a stroke will usually let patients control the upper part of their faces. A person with a stroke will usually have some wrinkling of their forehead.

One disease that may be difficult to exclude in the differential diagnosis is involvement of the facial nerve in infections with the herpes zoster virus. The major differences in this condition are the presence of small blisters, or "vesicles", on the external ear and hearing disturbances, but these findings may occasionally be lacking (zoster sine herpete). Reactivation of existing herpes zoster infection leading to facial paralysis in a Bell's palsy type pattern is known as Ramsay Hunt syndrome type 2.

Lyme disease may produce facial palsy. Sometimes the facial palsy occurs at the same time as the classic erythema migrans rash. Other times, it occurs later. In areas where Lyme disease is common, it may be the cause of facial palsy in half of cases.

Facial nerve paralysis is characterised by unilateral facial weakness, with other symptoms including loss of taste, , and decreased salivation and tear secretion. Other signs may be linked to the cause of the paralysis, such as s in the ear, which may occur if the facial palsy is due to shingles. Symptoms may develop over several hours. Acute facial pain radiating from the ear may precede the onset of other symptoms.

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.

People with the spastic/spasticity type of CP are hypertonic—i.e., they present with very stiff and tight muscle groups, far greater than typical humans—and have what is essentially a neuromuscular mobility impairment (rather than hypotonia or paralysis) which stems from an upper motor neuron lesion in the brain. The corticospinal tract or the motor cortex may be secondarily affected.

Spastic muscles are continuously contracting, or "tight", because the corresponding nerves permanently over-fire the command to tighten. This is caused by their inability to properly absorb GABA, or gamma amino butyric acid. The tightness, in addition to restricting movement, also acts as an overwhelming opposing force to neighbouring muscles and joints, eventually leaving the entire skeleton deformed compared to normal skeletal, bone, and joint structure in people without spasticity. Abnormal postures are usually associated with the antigravity muscles, which are extensors in the leg and the flexors in the arm. Deformities of joints develop which may become joint contractures, or "fixed contractures", with time.

Changes in spasticity and corresponding postures may also occur with other brain activity, such as excitement, fear or anxiety, or even pain, which increase muscle tension.

A person with spastic CP will commonly show, in addition to higher muscle tone, persistent primitive reflexes, greater stretch reflexes, plantar reflex, and ankle clonus.

A third of people with cerebral palsy have seizures - this is most common in spastic CP.

Ischemic stroke selectively affects somatic fibers over parasympathetic fibers, while traumatic stroke affects both types more equally. Therefore, while almost all forms cause ptosis and impaired movement of the eye, pupillary abnormalities are more commonly associated with trauma than with ischemia.

Oculomotor palsy can be of acute onset over hours with symptoms of headache when associated with diabetes mellitus. Diabetic neuropathy of the oculomotor nerve in a majority of cases does not affect the pupil. The sparing of the pupil is thought to be associated with the microfasciculation of the edge fibers which control the pupillomotor fibers, which control the pupil.

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.

Oculomotor nerve palsy or third nerve palsy is an eye condition resulting from damage to the third cranial nerve or a branch thereof. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements. Thus, damage to this nerve will result in the affected individual being unable to move his or her eye normally. In addition, the nerve also supplies the upper eyelid muscle (levator palpebrae superioris) and the muscles responsible for pupil constriction (sphincter pupillae) . The limitations of eye movements resulting from the condition are generally so severe that the affected individual is unable to maintain normal alignment of their eyes when looking straight ahead, leading to strabismus and, as a consequence, double vision (diplopia).

It is also known as "oculomotor neuropathy".

Prognosis for PBP patients is poor. Progressive bulbar palsy symptoms can include progressive difficulty with chewing, talking, and swallowing. Patients can also exhibit reduced gag reflexes, weak palatal movements, fasciculations, and weak movement of the facial muscles and tongue. In advanced cases of PBP, the patient may be unable to protrude their tongue or manipulate food in their mouth.

Patients with early cases of PBP have difficulty with pronunciations, particularly lateral consonants (linguals) and velars, and may show problems with drooling saliva. If the corticobulbar tract is affected a pseudobulbar affect with emotional changes may occur. Because PBP patients have such difficulty swallowing, food and saliva can be inhaled into the lungs. This can cause gagging and choking, and it increases the risk of pneumonia. Death, which is often from pneumonia, usually occurs 1 to 3 years after the start of the disorder.

The upper motor neuron lesion in the brain impairs the ability of some nerve receptors in the spine to properly receive gamma amino butyric acid (GABA). That leads to hypertonia in the muscles signaled by those damaged nerves. The limbs and body areas in which hypertonia manifests can be any or even all of them, depending which specific nerve groupings within the spine are rendered unable to receive GABA. Thus, spastic CP is often designated by body topography.

Individuals with spastic diplegia are very tight and stiff and must work very hard to successfully resist and "push through" the extra tightness they perpetually experience. Other than this, however, these individuals are almost always normal in every significant clinical sense. When they are younger, spastic diplegic individuals typically undergo gait analysis so that their clinicians can determine the best assistive devices for them, if any are necessary, such as a walker or crutches. The main difference between spastic diplegia and a normal gait pattern is its signature "scissor gait"—a style that some able-bodied people might tend to confuse with the effects of drunkenness, multiple sclerosis, or another nerve disease. The degree of spasticity in spastic diplegia (and, for that matter, other types of spastic CP) varies widely from person to person. No two people with spastic diplegia are exactly alike. Balance problems and/or stiffness in gait can range from barely noticeable all the way to misalignments so pronounced that the person needs crutches (typically forearm crutches/lofstrand crutches) or a cane / walking stick to assist in ambulation. Less often, spasticity is severe enough to compel the person to use a wheelchair. In general, however, lower-extremity spasticity in spastic diplegia is rarely so great as to totally prevent ambulation—most people with the condition can walk, and can do so with at least a basic amount of overall stability. Regardless, it should be noted that from case to case, steeply varying degrees of imbalance, potential tripping over uneven terrain while walking, or needing to hold on to various surfaces or walls in certain circumstances to keep upright, are typically ever-present potential issues and are much more common occurrences amongst those with spastic diplegia than among those with a normal or near-normal gait pattern. Among some of the people with spastic diplegia who choose to be ambulatory on either an exclusive or predominant basis, one of the seemingly common lifestyle choices is for the person to ambulate within his or her home without an assistive device, and then to use the assistive device, if any, once outdoors. Others may use no assistive device in any "indoor" situation at all, while always using one when outdoors. Above the hips, persons with spastic diplegia typically retain normal or near-normal muscle tone and range of motion, though some lesser spasticity may also affect the upper body, such as the trunk and arms, depending on the severity of the condition in the individual (the spasticity condition affecting the whole body equally, rather than just the legs, is spastic quadriplegia, a slightly different classification). In addition, because leg tightness often leads to instability in ambulation, extra muscle tension usually develops in the shoulders, chest, and arms due to compensatory stabilisation movements, regardless of the fact that the upper body itself is not directly affected by the condition.

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.

Spastic diplegia, historically known as Little's Disease, is a form of cerebral palsy (CP) that is a chronic neuromuscular condition of hypertonia and spasticity—manifested as an especially high and constant "tightness" or "stiffness"—in the muscles of the lower extremities of the human body, usually those of the legs, hips and pelvis. Doctor William John Little's first recorded encounter with cerebral palsy is reported to have been among children who displayed signs of spastic diplegia.

Spastic diplegia accounts for about 22% of all diagnoses of cerebral palsy, and together with spastic quadriplegia and spastic triplegia make up the broad classification spastic cerebral palsy, which accounts for 70% of all cerebral palsy diagnoses.

Differential diagnosis is rarely difficult in adults. Onset is typically sudden with symptoms of horizontal diplopia. Limitations of eye movements are confined to abduction of the affected eye (or abduction of both eyes if bilateral) and the size of the resulting convergent squint or esotropia is always larger on distance fixation - where the lateral rectii are more active - than on near fixation - where the medial rectii are dominant. Abduction limitations which mimic VIth nerve palsy may result secondary to surgery, to trauma or as a result of other conditions such as myasthenia gravis or thyroid eye disease.

In children, differential diagnosis is more difficult because of the problems inherent in getting infants to cooperate with a full eye movement investigation. Possible alternative diagnosis for an abduction deficit would include:

1. Mobius syndrome - a rare congenital disorder in which both VIth and VIIth nerves are bilaterally affected giving rise to a typically 'expressionless' face.

2. Duane's syndrome - A condition in which both abduction and adduction are affected arising as a result of partial innervation of the lateral rectus by branches from the IIIrd oculomotor cranial nerve.

3. Cross fixation which develops in the presence of infantile esotropia or nystagmus blockage syndrome and results in habitual weakness of lateral rectii.

4. Iatrogenic injury. Abducens nerve palsy is also known to occur with halo orthosis placement.The resultant palsy is identified through loss of lateral gaze after application of the orthosis and is the most common cranial nerve injury associated with this device.

The nerve dysfunction induces esotropia, a convergent squint on distance fixation. On near fixation the affected individual may have only a latent deviation and be able to maintain binocularity or have an esotropia of a smaller size. Patients sometimes adopt a face turned towards the side of the affected eye, moving the eye away from the field of action of the affected lateral rectus muscle, with the aim of controlling diplopia and maintaining binocular vision.

Diplopia is typically experienced by adults with VI nerve palsies, but children with the condition may not experience diplopia due to suppression. The neuroplasticity present in childhood allows the child to 'switch off' the information coming from one eye, thus relieving any diplopic symptoms. Whilst this is a positive adaptation in the short term, in the long term it can lead to a lack of appropriate development of the visual cortex giving rise to permanent visual loss in the suppressed eye; a condition known as amblyopia.

Though present from birth, symptoms of congenital fourth cranial nerve palsy may start as subtle and increase with age. Hence, diagnosis by a healthcare practitioner may not be made until later childhood or adulthood. Young children adopt a compensatory head position in order to compensate for the underacting superior oblique muscle. The characteristic head tilt is usually away from the affected side to reduce eye strain and prevent double vision (diplopia). Old photographs may reveal the presence of a consistent head tilt (ocular torticollis) from an early age. Most patients with congenital CN IV palsy have facial asymmetry due to the chronic head tilt. Other compensatory measures for congenital fourth nerve palsy are development of large vertical fusional amplitudes and lack of subjective symptoms of , even in the presence of great ocular rotation.

Congenital fourth nerve palsy may remain undetected until adulthood, when intermittent diplopia may arise, due to decompensated ability to overcome the vertical deviation. Until this occurs, many ophthalmologists and optometrists may miss the other signs and symptoms. Reduced vertical fusional reserves result from fatigue (stress, fever, other illnesses, a lot of near work) or simply the effects of old age. Diplopia from congenital fourth nerve palsy has occasionally been reported to manifest transiently during pregnancy. Congenital fourth nerve palsy may also become evident following cataract surgery once binocular vision is restored after a long period of progressive monocular visual loss and accompanying vergence decompensation. Other adult patients complain of neck pain, after years of chronic head tilting (ocular torticollis).

Congenital fourth nerve palsy can affect reading comprehension (and concentration during other near tasks) due to the increased vertical fusional demands and head tilting required to maintain single vision and prevent vertical diplopia. Some patients find they lose their place easily while reading, and find a marker or using a finger to guide them helpful.

The head posture is right 4th nerve palsy can be easily understood by this thumb rule- The body performs the action which the paralysed muscle had to perform. Keeping this thumb rule in mind, let us decipher the head posture in right 4th nerve palsy. As SO causes intorsion, the head tilts towards the left. As SO causes depression in adduction, the head turns towards left and depressed chin. So the patient has left side deflection, tilt and a downward gaze. The left SO palsy head posture can be understood similarly as well.

- "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.

Progressive bulbar palsy (PBP) is a medical condition. It belongs to a group of disorders known as motor neuron diseases. PBP is a disease that attacks the nerves supplying the bulbar muscles. These disorders are characterized by the degeneration of motor neurons in the cerebral cortex, spinal cord, brain stem, and pyramidal tracts. This specifically involves the glossopharyngeal nerve (IX), vagus nerve (X), and hypoglossal nerve (XII).

This disorder should not be confused with pseudobulbar palsy or progressive spinal muscular atrophy. The term Infantile progressive bulbar palsy is used to describe progressive bulbar palsy in children. Some neurologists consider this disorder to be a subset of amyotrophic lateral sclerosis (ALS), but others disagree with that classification.

In addition, there may be lower motor neuron lesions of the limbs.

The ocular muscles are spared and this differentiates it from myasthenia gravis.

The appearance of the affected arm (or arms) depends on the individual case. In some cases the arm may lack the ability to straighten or rotate but otherwise function normally giving the overall appearance of the arm to be stiff and crooked. Whereas in other circumstances the arm has little to no control and has a "loose" appearance. Treatment such as physiotherapy, massage and electrical stimulation can help to prevent this early on (or throughout) the patient's life by strengthening the arm.

In some cases, again, individuals may suffer a great deal of discomfort. For example, they may experience a severe cramping pain that lasts for some time and is particularly painful after they have slept, running from the shoulder all the way down to the wrist. Although pain does not affect everyone with Erb's Palsy, it can be extremely uncomfortable to those that it does and can even cause patients to be physically sick or faint. This extreme nerve pain is mostly common during the final stages of growth and almost always eases off in time. Other pains that Erb's Palsy sufferers might endure include strained muscle, stiffness, circulatory problems and cramp. Different factors are dependent on the severity of the condition and can vary, so whilst some patient experience a lot of pain, some patients may experience no pain at all and for their affected arm to simply be visually crooked.

Discomfort with the shoulder blade is also extremely common in Erb's palsy as the shoulder is often at risk of dislocation. This can result, again, in sickness or lack of sleep.

Axillary nerve palsy patients present themselves with differing symptoms. For instance, some axillary nerve palsy patients complain that they cannot bend their arm at the elbow, however no other pain or discomfort exists. To further complicate diagnosis, onset of palsy can be delayed and may not be noticed until 12-24 hours after the trauma of shoulder region occurred. Therefore it is important to recognize the symptoms, but also to realize that different people have various combinations of them.

Symptoms include:

- cannot bend arm at the elbow

- deficiency of deltoid muscle function

- different regions of skin around the deltoid area can lack sensation

- unable to raise arm at the shoulder

Spastic hemiplegia is a neuromuscular condition of spasticity that results in the muscles on one side of the body being in a constant state of contraction. It is the "one-sided version" of spastic diplegia. It falls under the mobility impairment umbrella of cerebral palsy. About 20–30% of people with cerebral palsy have spastic hemiplegia. Due to brain or nerve damage, the brain is constantly sending action potentials to the neuromuscular junctions on the affected side of the body. Similar to strokes, damage on the left side of the brain affects the right side of the body and damage on the right side of the brain affects the left side of the body.

The affected side of the body is rigid, weak and has low functional abilities. In most cases, the upper extremity is much more affected than the lower extremity. This could be due to preference of hand usage during early development. If both arms are affected, the condition is referred to as double hemiplegia. Some patients with spastic hemiplegia only suffer minor impairments, where in severe cases one side of the body could be completely paralyzed. The severity of spastic hemiplegia is dependent upon the degree of the brain or nerve damage.

Conjugate gaze palsies can be classified into palsies affecting horizontal gaze and vertical gaze.

Infants with spastic hemiplegia may develop a hand preference earlier than is typical.