From the Guidelines

Central and peripheral nystagmus have distinct characteristics.

Peripheral nystagmus is typically associated with benign paroxysmal positional vertigo (BPPV) and is triggered by specific head movements, such as the Dix-Hallpike maneuver 1.
Central nystagmus, on the other hand, is often associated with more ominous causes, such as mass lesions, hemorrhage, infarct, and demyelinating disease, and may present with symptoms of acute vestibular syndrome (AVS) 1.

Direction of nystagmus: Peripheral nystagmus is typically unidirectional, while central nystagmus can be bidirectional or multidirectional 1.
Presence of other symptoms: Central nystagmus is often accompanied by other neurologic symptoms, such as headache, photophobia, or phonophobia, while peripheral nystagmus is typically isolated to vertigo and nystagmus 1.

HINTS examination: A bedside test that can help distinguish between peripheral and central causes of nystagmus, with a high sensitivity for detecting posterior circulation infarct 1.
Imaging: May be required to rule out central causes of nystagmus, such as stroke or mass lesions, especially if the HINTS examination is positive or if there are atypical features present 1.

From the Research

Central nystagmus is defined as rhythmic, most often involuntary eye movements, which normally consist of a slow (pathological) drift of the eyes and a fast central compensatory movement of the eyes back to the primary position (re-fixation saccade) 2, 3
The direction of nystagmus is reported according to the fast phase 2
Central nystagmus can be spontaneous, occurring in the primary position, or induced by certain factors such as gaze, head-shaking, or positional changes 2, 3
Peripheral nystagmus, on the other hand, is often caused by vestibular disorders, such as benign paroxysmal positional vertigo (BPPV) 4, 5

Downbeat nystagmus: most often caused by a bilateral floccular lesion or dysfunction 2, 3
Upbeat nystagmus: caused by a lesion in the midbrain or medulla 2, 3
Infantile nystagmus: a type of nystagmus that occurs in infants 2, 3
Pure torsional nystagmus: a type of nystagmus that occurs in the torsional plane 2, 3
Pendular fixation nystagmus: a type of nystagmus that occurs in patients with visual fixation 2, 3
Periodic alternating nystagmus: a type of nystagmus that occurs in a periodic and alternating pattern 2, 3
Seesaw nystagmus: a type of nystagmus that occurs in a seesaw pattern 2, 3

Diagnosis is based on a systematic clinical examination of all types of eye movements, including spontaneous nystagmus, range of eye movements, smooth pursuit, saccades, gaze-holding function, vergence, optokinetic nystagmus, and testing of the function of the vestibulo-ocular reflex (VOR) and visual fixation suppression of the VOR 3
Treatment includes pharmacotherapy, such as 4-aminopyridine for downbeat and upbeat nystagmus, memantine or gabapentin for pendular fixation nystagmus, or baclofen for periodic alternating nystagmus 2, 3, 5

The spatial position of the nystagmus vector can be used to determine the site of origin of the disease that causes nystagmus, with "uphill" nystagmus likely being peripheral and "downhill" nystagmus likely being central 6
The head impulse test (HIT) can also be used to confirm the diagnosis of central or peripheral nystagmus 6