The conditions
Tumours & other central causes
Tumours of the posterior fossa rarely announce themselves with pure vertigo. They tend to erode balance slowly, alongside cranial-nerve and cerebellar signs — and the danger is less the dizziness than the mass behind it.
How tumours cause vertigo
A tumour is an abnormal growth. When one grows at the back of the head — near the balance nerves, the brainstem or the cerebellum — it can press on the balance pathways and cause unsteadiness or, less often, true spinning. Because it grows slowly, the body often adapts, so the main complaints may be gradual imbalance, hearing change, or headache rather than sudden vertigo.
Tumours produce vertigo by compressing or infiltrating the central vestibular pathways in the posterior fossa, or the vestibular nerve at the cerebellopontine angle. Their slow growth usually allows central compensation, so the presentation is more often progressive disequilibrium with localising signs than the explosive vertigo of stroke or the relapsing vertigo of MS.4
The clinically important distinction is tempo and company. Vertigo that is slowly progressive, accompanied by cranial-nerve (V, VII, VIII) or cerebellar signs, or by features of raised intracranial pressure (morning headache, papilloedema, vomiting), should move a posterior-fossa mass up the differential and trigger contrast-enhanced MRI. The acute emergency is not the tumour itself but its mass effect on the fourth ventricle and brainstem.2
Cerebellopontine-angle tumours
The commonest mass at the cerebellopontine angle is the vestibular schwannoma (acoustic neuroma), a benign Schwann-cell tumour of the vestibulocochlear nerve. It typically causes asymmetric sensorineural hearing loss and tinnitus with chronic imbalance rather than acute rotational vertigo, because the slow loss of vestibular input is centrally compensated.1 As it enlarges it can compress the trigeminal nerve (facial numbness, reduced corneal reflex), the facial nerve, and finally the brainstem and cerebellum. Meningiomas and epidermoids occur at the same site and present similarly. Although the schwannoma itself is a peripheral nerve tumour, it belongs in any discussion of central causes because it is the key posterior-fossa mass to exclude in unexplained imbalance — and it is covered in detail in its own context elsewhere in the atlas.
Cerebellar and brainstem tumours
Intra-axial posterior-fossa tumours sit directly within the vestibular machinery:
- Cerebellar tumours — in adults, metastases and haemangioblastoma; in children, medulloblastoma, pilocytic astrocytoma and ependymoma. They cause gait and limb ataxia, gaze-evoked or downbeat nystagmus, and disequilibrium.
- Brainstem gliomas — infiltrate the vestibular nuclei and ocular-motor pathways, producing central vertigo with multiple cranial-nerve and long-tract signs.
- Fourth-ventricular tumours — ependymoma and others can obstruct CSF flow, adding positional vertigo and the features of raised intracranial pressure.
A growing posterior-fossa mass shares the cardinal hazard of a large cerebellar infarct: compression of the fourth ventricle with obstructive hydrocephalus and brainstem compression, which is the event that turns a chronic problem into an emergency.2
Other and rarer central causes
Beyond the three headline conditions, several other central processes can present with vertigo and are worth keeping in mind when the picture does not fit:
- Paraneoplastic cerebellar degeneration — subacute cerebellar syndrome with vertigo and downbeat nystagmus, sometimes preceding the underlying cancer; associated with onconeural antibodies (e.g. anti-Yo, anti-Hu).3
- Chiari malformation — cerebellar tonsillar descent causing downbeat nystagmus and cough-induced or positional vertigo.
- Posterior-fossa haemorrhage, abscess and demyelinating tumefactive lesions — space-occupying mimics of tumour.
- Episodic ataxia and degenerative cerebellar disease — channelopathies and spinocerebellar ataxias causing recurrent or progressive central vertigo.
Bottom line: suspect a posterior-fossa mass when vertigo is slowly progressive, comes with cranial-nerve or cerebellar signs, or carries features of raised intracranial pressure — and image with contrast-enhanced MRI.
Key points
- Posterior-fossa tumours usually cause progressive disequilibrium with localising signs, not isolated acute vertigo.
- Vestibular schwannoma is the key CPA mass — asymmetric hearing loss and imbalance more than true vertigo.
- Cerebellar, brainstem and fourth-ventricular tumours produce central nystagmus, ataxia and, when they obstruct CSF, raised intracranial pressure.
- The emergency is mass effect — hydrocephalus and brainstem compression — not the tumour per se.
- Keep paraneoplastic degeneration, Chiari malformation and degenerative cerebellar disease in mind for atypical pictures.