Nystagmus is a condition of involuntary, repetitive eye movements. These movements can be rapid or slow, and they often lead to reduced vision and a sensation of imbalance. The term itself describes a rhythmic oscillation of the eyes that a person cannot consciously control.

Spontaneous Nystagmus

Spontaneous nystagmus occurs without any obvious external trigger. It appears when the head is stationary and the person is looking straight ahead. This form of nystagmus is often a key sign in distinguishing between different underlying disorders. When evaluating a patient, clinicians note the direction, frequency, and amplitude of the movement. Spontaneous nystagmus may be constant or may change with gaze direction, and it frequently accompanies feelings of dizziness.

Pendular and Jerk Nystagmus

Nystagmus is broadly divided into two types based on the waveform of the eye movement.

Pendular nystagmus involves smooth, sinusoidal oscillations of the eyes, where the movement is equal in speed and amplitude in both directions. It resembles the swing of a pendulum. This type is often associated with conditions that affect visual fixation, such as albinism, or with lesions in the brainstem or cerebellum.

Jerk nystagmus is more common and features a slow drifting phase in one direction followed by a quick corrective saccade in the opposite direction. The direction of jerk nystagmus is conventionally named after the fast phase. It can be horizontal, vertical, or torsional. Jerk nystagmus is frequently seen in vestibular disorders and is a hallmark of peripheral or central imbalance.

Nystagmus and Dizziness

Dizziness is a common complaint among individuals with nystagmus. The two symptoms are closely linked because both arise from the vestibular system and its connections to the brainstem and cerebellum. When nystagmus is present, the brain receives conflicting signals about head position and motion, which can trigger a sensation of spinning, unsteadiness, or lightheadedness.

In acute vestibular conditions, the onset of dizziness and nystagmus is often sudden. The relationship between the two helps clinicians identify whether the source of the problem lies in the inner ear or in the brain.

Central versus Peripheral Nystagmus

A critical step in evaluating nystagmus is determining whether it is central or peripheral in origin.

Peripheral nystagmus arises from dysfunction of the vestibular apparatus or the vestibular nerve. It is typically horizontal or torsional, is suppressed by visual fixation, and is accompanied by significant dizziness, hearing loss, or tinnitus. Benign paroxysmal positional vertigo and vestibular neuritis are common examples.

Central nystagmus originates from lesions in the brainstem, cerebellum, or other central nervous system structures. It can be vertical, purely torsional, or purely horizontal. Unlike peripheral forms, central nystagmus is often not suppressed by fixation and may not be associated with hearing symptoms. Dizziness in central nystagmus is usually less intense but may be accompanied by other neurological signs such as ataxia, dysarthria, or weakness.

Recognising the difference is essential because central nystagmus may indicate serious conditions such as stroke, multiple sclerosis, or structural lesions, whereas peripheral nystagmus is often benign and self-limiting.

Evaluation and Management

Assessment of nystagmus includes a thorough clinical history, observation of eye movements, and a neurological examination. Bedside tests such as the head impulse test, gaze-holding test, and positional manoeuvres help differentiate between types. Instrumentation such as video-oculography and electronystagmography can provide precise recordings of the eye movements.

Management depends on the underlying cause. Peripheral causes are often treated with vestibular rehabilitation, positional manoeuvres, or medications that suppress vestibular activity. Central causes require prompt investigation and treatment of the underlying neurological condition. Symptomatic relief for the associated dizziness may include medications that dampen vestibular responses.