The first symptoms of Guillain–Barré syndrome are numbness, tingling, and pain, alone or in combination. This is followed by weakness of the legs and arms that affects both sides equally and worsens over time. The weakness can take half a day to over two weeks to reach maximum severity, and then becomes steady. In one in five people, the weakness continues to progress for as long as four weeks. The muscles of the neck may also be affected, and about half experience involvement of the cranial nerves which supply the head and face; this may lead to weakness of the muscles of the face, swallowing difficulties and sometimes weakness of the eye muscles. In 8%, the weakness affects only the legs (paraplegia or paraparesis). Involvement of the muscles that control the bladder and anus is unusual. In total, about a third of people with Guillain–Barré syndrome continue to be able to walk. Once the weakness has stopped progressing, it persists at a stable level ("plateau phase") before improvement occurs. The plateau phase can take between two days and six months, but the most common duration is a week. Pain-related symptoms affect more than half, and include back pain, painful tingling, muscle pain and pain in the head and neck relating to irritation of the lining of the brain.

Many people with Guillain–Barré syndrome have experienced the signs and symptoms of an infection in the 3–6 weeks prior to the onset of the neurological symptoms. This may consist of upper respiratory tract infection (rhinitis, sore throat) or diarrhea.

In children, particularly those younger than six years old, the diagnosis can be difficult and the condition is often initially mistaken (sometimes for up to two weeks) for other causes of pains and difficulty walking, such as viral infections, or bone and joint problems.

On neurological examination, characteristic features are the reduced power and reduced or absent tendon reflexes (hypo- or areflexia, respectively). However, a small proportion has normal reflexes in affected limbs before developing areflexia, and some may have exaggerated reflexes. In the "Miller Fisher variant" subtype of Guillain–Barré syndrome (see below), a triad of weakness of the eye muscles, abnormalities in coordination, as well as absent reflexes can be found. The level of consciousness is normally unaffected in Guillain–Barré syndrome, but the Bickerstaff brainstem encephalitis subtype may feature drowsiness, sleepiness, or coma.

A quarter of all people with Guillain–Barré syndrome develop weakness of the breathing muscles leading to respiratory failure, the inability to breathe adequately to maintain healthy levels of oxygen and/or carbon dioxide in the blood. This life-threatening scenario is complicated by other medical problems such as pneumonia, severe infections, blood clots in the lungs and bleeding in the digestive tract in 60% of those who require artificial ventilation.

In order to diagnose Bickerstaff brainstem encephalitis, ataxia and ophthalmoplegia must be present. These are also diagnostic features of Miller Fisher syndrome, and so Bickerstaff's is only diagnosed if other features are present which exclude Miller Fisher syndrome. These may include drowsiness, coma or hyperreflexia. When the condition is defined in this way, a number of other features are commonly but not always found: among these are weakness of the limbs, the face, and/or the bulbar muscles; abnormalities of the pupils; and absent reflexes.

Like some other autoimmune diseases, the condition usually follows a minor infection, such as a respiratory tract infection or gastroenteritis.

Bickerstaff brainstem encephalitis is a rare inflammatory disorder of the central nervous system, first described by Edwin Bickerstaff in 1951. It may also affect the peripheral nervous system, and has features in common with both Miller Fisher syndrome and Guillain–Barré syndrome.

BVVL is marked by a number of cranial nerve palsies, including those of the motor components involving the 7th and 9th-12th cranial nerves, spinal motor nerves, and upper motor neurons. Major features of BVVL include facial and neck weakness, fasciculation of the tongue, and neurological disorders from the cranial nerves. The neurological manifestations develop insidiously: they usually begin with sensorineural deafness, progress inexorably to paralysis, and often culminate in respiratory failure. Most mortality in patients has been from either respiratory infections or respiratory muscle paralysis. Pathological descriptions of BVVL include injury and depletion of 3rd-7th cranial nerves, loss of the spinal anterior horn cells, degeneration of Purkinje cells, as well as degeneration of the spinocerebellar and pyramidal tracts. The first symptoms in nearly all cases of BVVL is progressive vision loss and deafness, and the first initial symptoms are seen anywhere from one to three years.

Most cases of deafness are followed by a latent period that can extend anywhere from weeks to years, and this time is usually marked by cranial nerve degeneration. Neurological symptoms of BVVL include optic atrophy, cerebellar ataxia, retinitis pigmentosa, epilepsy and autonomic dysfunction. Non-neurological symptoms can include diabetes, auditory hallucinations, respiratory difficulties, color blindness, and hypertension.

Brown-Vialetto-Van-Laere syndrome (BVVL), sometimes known as Brown's Syndrome, is a rare degenerative disorder often initially characterized by progressive sensorineural deafness.

The syndrome most often affects children, adolescents, and young adults. As knowledge of BVVL grows some adult patients have now been diagnosed. There is no known cure, however with prompt treatment the prognosis may be positive with some patients stabilizing and even minor improvements noted in certain cases.

This is characterized by hand and arm abnormalities. The following are specific characteristics:

- Malformed or absent (aplasia) thumb

- A thumb that looks more like a finger

- Partial or complete absence of a radius

- Shortening and radial deviation of the forearms

- Triphalangeal thumb

- Duplication of the thumb (preaxial polydactyly)

People with the combination of Duane anomaly and radial ray malformations may have a variety of other signs and symptoms. These features include:

- Unusually shaped ears

- Hearing loss

- Heart and kidney defects

- A distinctive facial appearance

- An inward- and downward-turning foot (a clubfoot)

- Fused vertebrae.

Neurological abnormalities are common. Roughly 45% of people with Parry–Romberg syndrome are also afflicted with trigeminal neuralgia (severe pain in the tissues supplied by the ipsilateral trigeminal nerve, including the forehead, eye, cheek, nose, mouth and jaw) and/or migraine (severe headaches that may be accompanied by visual abnormalities, nausea and vomiting).

10% of affected individuals develop a seizure disorder as part of the disease. The seizures are typically Jacksonian in nature (characterized by rapid spasms of a muscle group that subsequently spread to adjacent muscles) and occur on the side contralateral to the affected side of the face. Half of these cases are associated with abnormalities in both the gray and white matter of the brain—usually ipsilateral but sometimes contralateral—that are detectable on magnetic resonance imaging (MRI) scan.

Enophthalmos (recession of the eyeball within the orbit) is the most common eye abnormality observed in Parry–Romberg syndrome. It is caused by a loss of subcutaneous tissue around the orbit. Other common findings include drooping of the eyelid (ptosis), constriction of the pupil (miosis), redness of the conjunctiva, and decreased sweating (anhidrosis) of the affected side of the face. Collectively, these signs are referred to as Horner's syndrome. Other ocular abnormalities include ophthalmoplegia (paralysis of one or more of the extraocular muscles) and other types of strabismus, uveitis, and heterochromia of the iris.

Individuals with KSS present initially in a similar way to those with typical CPEO. Onset is in the first and second decades of life.

The first symptom of this disease is a unilateral ptosis, or difficulty opening the eyelids, that gradually progresses to a bilateral ptosis. As the ptosis worsens, the individual commonly extends their neck, elevating their chin in an attempt to prevent the eyelids from occluding the visual axis. Along with the insidious development of ptosis, eye movements eventually become limited causing a person to rely more on turning the head side to side or up and down to view objects in the peripheral visual field.

FLD produces rapidly progressive weakness of tongue, face and pharyngeal muscles in a clinical pattern similar to myasthenia. Neuromuscular transmission may be abnormal in these muscles because of rapid denervation and immature reinnervation. Paralysis occurs secondary to degeneration of the motor neurons of the brain stem. It causes progressive bulbar paralysis due to involvement of motor neurons of the cranial nerve nuclei. The most frequent symptoms at onset of progressive bulbar paralysis of childhood has been a unilateral facial paralysis. It is followed in frequency by dysarthria due to facial weakness or by dysphagia. Palatal weakness and palpebral ptosis also have been reported in few patients. Both sexes can be affected.

Fazio–Londe disease (FLD), also called progressive bulbar palsy of childhood, is a very rare inherited motor neuron disease of children and young adults and is characterized by progressive paralysis of muscles innervated by cranial nerves.

KSS results in a pigmentation of the retina, primarily in the posterior fundus. The appearance is described as a "salt-and-pepper" appearance. There is diffuse depigmentation of the retinal pigment epithelium with the greatest effect occurring at the macula. This is in contrast to retinitis pigmentosa where the pigmentation is peripheral. The appearance of the retina in KSS is similar to that seen in myotonic dystrophy type 1 (abbreviated DM1). Modest night-blindness can be seen in patients with KSS. Visual acuity loss is usually mild and only occurs in 40–50% of patients.

This produces ipsilateral horizontal gaze palsy and facial nerve palsy and contralateral hemiparesis, hemisensory loss, and internuclear ophthalmoplegia.

Symptoms of MMND begin appearing when people are young, often before the age of 15. An affected individual is generally thin with weak arms and legs. They may lose control of the muscles that control their face, mouth, nose, and throat. This in turn, will cause difficulties speaking and swallowing. Further complications from the loss of facial motor control include drooling, as well facial droop. People with MMND may also suffer from a loss of hearing and sight.

Foville's syndrome is caused by the blockage of the perforating branches of the basilar artery in the region of the brainstem known as the pons. Most frequently caused by vascular disease or tumors involving the dorsal pons.[3]

Structures affected by the infarct are the PPRF, nuclei of cranial nerves VI and VII, corticospinal tract, medial lemniscus, and the medial longitudinal fasciculus. There's involvement of the fifth to eighth cranial nerves, central sympathetic fibres (Horner syndrome) and horizontal gaze palsy.[3]

Manifestations include enlarged viscera, hepatomegaly, diabetes, short stature and cranial hyperostosis.

People with Möbius syndrome are born with facial paralysis and the inability to move their eyes laterally. Often, the upper lip is retracted due to muscle shrinkage. Occasionally, the cranial nerves V and VIII are affected. If cranial nerve VIII is affected, the person experiences hearing loss.

Other symptoms that sometimes occur with Möbius syndrome are:

- Limb abnormalities—clubbed feet, missing fingers or toes

- Chest-wall abnormalities (Poland Syndrome)

- Crossed eyes (strabismus)

- Difficulty in breathing and/or in swallowing

- Corneal erosion resulting from difficulty in blinking

Children with Möbius syndrome may have delayed speech because of paralysis of muscles that move the lips, soft palate, and tongue root. However, with speech therapy, most people with Möbius syndrome can develop understandable speech. Möbius syndrome has been associated with increased occurrence of the symptoms of autism. However, some children with Möbius syndrome are mistakenly labeled as intellectually disabled or autistic because of their expressionless faces, strabismus, and frequent drooling.

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

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

Signs and symptoms include:

- syndromic facies

- hearing loss

- facial paralysis

Katz Syndrome is a rare congenital disorder, presenting as a polymalformative syndrome characterized by enlarged viscera, hepatomegaly, diabetes, and skeletal anomalies that result in a short stature, cranial hyperostosis, and typical facial features. It is probably a variant of the autosomal recessive type of Craniometaphyseal Dysplasia.

In contrast, pseudobulbar palsy is a clinical syndrome similar to bulbar palsy but in which the damage is located in upper motor neurons of the corticobulbar tracts in the mid-pons (i.e., in the cranial nerves IX-XII), that is the nerve cells coming down from the cerebral cortex innervating the motor nuclei in the medulla. This is usually caused by stroke.

Madras motor neuron disease (MMND) is a motor neuron disease affecting primarily lower motor neurons. It is similar to Monomelic amyotrophy and primarily affects young adults in southern India.

Authors of a large case study, published in 2008, proposed that MMND be divided into two categories: spontaneously-arising MMND and Familial Madras Motor Neuron Disease (FMMND). Using this method, cases in which the disease is inherited would be categorized as FMMND, while cases that displayed no genetic linkage would be categorized as spontaneously-arising MMND.

According to the same study, there is a variant form known as MMNDV, which is classified by additional optic atrophy.

Due to the rareness of MMND, it is classified as a orphan disease.

The disease is characterised by bilateral diffuse uveitis, with pain, redness and blurring of vision. The eye symptoms may be accompanied by a varying constellation of systemic symptoms, such as auditory (tinnitus, vertigo, and hypoacusis), neurological (meningismus, with malaise, fever, headache, nausea, abdominal pain, stiffness of the neck and back, or a combination of these factors; meningitis, CSF pleocytosis, cranial nerve palsies, hemiparesis, transverse myelitis and ciliary ganglionitis), and cutaneous manifestations, including poliosis, vitiligo, and alopecia. The vitiligo often is found at the sacral region.